There is a wiring diagram on this website which shows all the engine compartment hookups.

Windshield glass is safety "laminated" and has clear plastic sandwiched between two sheets of glass to prevent breakage. Over time this plastic can degrade/discolor(heat&UV) and lose strength.
Glass is also susceptible to micro stress cracking over time, so one day it's just fine and the next day it has a crack propagating on one or both sides of the laminate depending on how it was stressed.
If you wash your car on a hot sunny day and the interior/glass gets real hot and then hit windshield with a cold water spray, this will tests it's "crackability". Wash in the shade if possible or while it's still cool.
Side glass sold now is usually "tempered" which makes it shatter, break into small pieces, when it breaks for safety reasons. Shards are deadly in a crash scenario. The older wreck photos, have alot to head imprints in the windshields from being thrown through the windshield, prior to seat belts.
I believe the glass on my '49 is laminated throughout, as the edges are getting yellow, so for the early models tempered wouldn't be "correct" but safer. Not sure what year they switched.
Folklore sez DuPont had a clear overliner material that prevents glass from breaking and it was rejected for cost reasons.
I worked on some glass chemical strengthening projects in my work daze. We made hot end coatings for bottles to prevent them from breaking during packaging and recycling and the Low E flat glass.

Nice 22 series '49, aka a '48 '49. I prefer those, they don't have the beltline chrome spear strips like a 23 '49. The bumpers appear to be '49, but the front doesn't show. If front has center cut outs and paint, it '48, if none, it's '49. Might just be rechromed or replaced?
I don't remember seeing yellow as a factory color, but I'll check.
It really makes no difference to the electrons which way they flow. But when you want them to do work, it does.
They went to 12V and negative ground to reduce wire size and decrease voltage drop impacts. This has been covered before. With 6V, you easily run into low voltage issues; slow starting, dim lights etc, and wire heating because of the increased amperage to get the same power. Properly installed and maintained 6V is not a problem.
To the budding polarity changer, you might have generator issues, if you just change the ground. Talk to an auto electric shop first. As it adds no value, may decrease it, I'd leave it alone, make it factory correct, as it'll cause confusion to subsequent owners like the first guy. If you make changes be sure to document them to stay with the car. eg; My other car had left hand thread lugs on the left side and the former owners tire jockey right hand impact wrench "idiots" couldn't get them off without busting most of them. So I changed them to rightie when I replaced the busted studs. That "L" stamp means left hand thread, if you know what it means, otherwise you torque away. The left spindle nut is another story so I have spare nuts for that to go with the car. I never stop getting amazed what people do to autos...

Compressor HP can be calculated*, but will depend on the size and type compressor, refrigerant gas, and how it's operated and mechanically linked/pulley ratios. If you're using a modern belt driven auto centrifugal compressor, you're roughly in the 5 HP range, if it's a period recip, up to 20. You should choose vendors based on efficiency.
Another thing to consider is the idle rpms. Maybe too low, for much cooling at stops without major re-pulleying.
Kinda why they didn't have much A/C back then until they improved the compression and HP with the OHV motors. Even a massive flat V12 was putting out about half as much HP, relatively speaking. And it only had to be a more comfortable mode than a horse or a bus to sell.
Depending on where you locate the hot side HX, it may or may not impact the radiator temp. If you put it in front of radiator, which it wasn't designed for, then you might have cooling issues. You can lower that temperature with the right refrigerant, but the EPA didn't hear me say that.
If you're not going to drive it much, adding more batteries, voltages, and alternators is more maintenance not justified. Hence the rise of the resto mod...or the leave it alone original.
* - should be listed by the vendor because that's essentially the "size" also.

If I'm not mistaken, there's also vacuum advance on the 288. So if that's not functioning, you'll not make power.

If you can swing it, I'd buy a whole 3 gun set. They come in handy, one for primer, one for small jobs, and a finish gun. I use an air brush for some things, mostly because I have it and when you don't want to drag out the big toys.
You can spend about as much money as you want here, but after a certain point it makes no sense, depending on use factor. I've got all kinds from over the years, but the new ones, with the replaceable cup seem to avoid some previous issues of cleanout. I've use more time and solvent cleaning than painting, especially with the catalyzed paints, like the new silicon motor paints.

That's just another thing you can thank Slick Willie Clinton for. His admin caved to ADM. Of course, he denies ever hearing of ethanol and there's no proof he'll say.

If you're a 6Volter, here's some candy to soothe your frustrations.
This months Cad/Lasalle publication, self-starter has an article, that resulted from some of their forum discussions.
They say to add a HD ground strap from the starter commutator to the battery ground attachment point and it cures slow starting even if you changed the cables, new battery, etc. Requires some mods, like removing and drilling commutator endplate for installing a 3/8 SS bolt for the lug for ground strap attachment. Other end of strap attaches to same point where battery grounds. Eliminates the voltage drop problems inherent of early 6V systems. If only the factory had thought of that...

When in doubt consult an expert. When still in doubt, let them do it. Go to an auto electric shop or the guy furnishing the alternator before you have a do it yourself meltdown.
Volts are measured in parallel and amps in series. Wire accordingly.
If the alternator has an internal voltage regulator, then you don't need the stock one and why it's jumped out. If you leave them both in, they'll buck each other.
Jumping out is the same as directly connecting wires up except just use the terminals to make the connections. Path of least resistance.

Another way to think about it is based on rpms. Each stroke or turn of the pump is producing a shot of oil. The faster the motor turns the more you need lubricant to the rotating and stroking parts and the more the pump delivers. eg; oil flows out on the cylinder wall on the up stroke and is wiped off in the down.
The gauge pressure is only showing the resistance to flow that's encountered, not the flow. Flow's pretty much fixed by the pump capacity. There's more resistance to flow the higher the flow in the same size channel. So gauge pressure will noramlly increase with rpms for these mechanical pumps up to a point.
No need to modify the viscosity. In fact, you might starve the pump inlet/pickup at lower temperatures with higher vis.
Diesels are a higher temperature and pressure animal producing more combustion soot/ash than a low compression '40's gasoline motor. So diesel lube requirements are much different and more severe. Use diesel grades for diesel service and gasoline grades for gasoline motors.
Your motor probably spec'ed out for ND 30W with leaded gas and some have filters and some don't. That was pretty much the most available refined motor oil grade at that time. The economics were to dump the contaminated oil frequently rather than make it last. Not same economics as we have today.
If you look at motor oil viscosity curves, you won't see as large a change in viscosity with temperature as the "W" numbering system suggests. In fact, they all get much thinner at operating temperature well below what you pour out the can.
I won't get into additives. I've addressed that one before.