I don't think there's any problem here. Either way.
I got a set of thrown out radials on the '49 to keep it mobile in the garage, and they hold just fine, been sitting peacefully for years now.
I think some riveted rims can present a leakage issue over time, due to crevice corrosion, etc.

Procedure is based on '50s understanding of thread torquing.
These values exceed the recommended ones for current 3/4 fine grade 5 of today.

I would gladly trade mine for the Provost motorhome...
It's more of a blues tune for me.

I think that's par for the course, rather than make separate model configs, they put "everything" on dash panel, then only hooked up what was optioned*. I recall having a few nonfunctional buttons, except radio was a delete panel.
It's just a little "different" to think backwards in positive ground terms, if hasn't been converted. Cloth wire is hardest to familiarize, if spent life in 12V (-) PVC shield world of colors.
I really need to decide what to do with my "P" project. Got a ton o money in it to sit a hulk and occupy parts shelves. The other one that wasn't supposed to come first is hopefully nearing the rebuild end. i"m working on it today AGAIN.
But that one even got way-layed by a new lease vehicle. Life interferes with best of plans. Kinda like that little shiny steel ball on the pinball table, sometimes it takes a whirl, makes lights and sounds, and sometimes goes straight down the drain...
* - unfortunately, unlike survivor brands, if one doesn't have a build sheet/other documentation in/on theirs, there's little way to find out "as delivered". That's even getting scarcer as paper is ephemera.

You should chase those threads before putting new bolts in.

The "dash 5" number on the plate indicates it's a '49 that was left over and sold as '50.
So check under the '49 paint codes also.

Most yellows fade, so unless it's been inside mostly, I doubt that is the original hue.
I guess I don't understand if you want to match the current color, paint original which probably won't match, or just trying to find out what color it might be?

That one is right up there with leaving the rotor out in frequency.
Some have read from the casting number instead of the firing order.
Good to admit and laugh it off.
Much "run to the internet" diagnostics these daze but that's because these are "old" technology, not everyone is "old" enough, and those that are can't recall.

We were commissioning a SOA control system, early '80s. The parts were so new, beta test, they didn't have documentation yet. So the supplier engr xeroed the pin out drawing, and it was mirror image, did not check. We plug in the ribbon cable, put the juice on, and chips popped like pop-corn - dead short. Chips were new and in short supply. Bosses don't have much humor for things like that, but they occur. All ended well and on time. Learned methodical the hard way.

A friend was taking flying lessons and he was not used to a "heading" compass. On solo, he ended up nearly out of fuel, heading 180 in wrong direction and had to declare an emergency at a major airport. So don't feel bad, yours wouldn't be fatal. He got the nickname "wrong way". I did ride with him once after licensed. I figured what's the chance on the first, but never do twice what you got away with once.

Call the Packard Museum in Warren, OH. They have some marine engines, documents, and restore so they can probably set you
right or put you in touch with someone. PAC is another source.

Didn't say if motor is in the car or on a stand?
Check your grounding, too.

From sound of things it's turning, spark, etc. So most likely either timing or fuel.
They'll run with most, not all the cylinders firing. New wires should work, so the connections are suspect, wrorng end clips, not engaged, etc.
If the battery is down and the starter warm, it may not be turning fast enough, but these run ~400 rpm at idle, so don't need much, but if battery is up and it's barely turning then the wiring to the starter and to and from the battery is not providing enough amps.
The carb starter has to be working or it won't turn at all - no juice to starter.
Anorher problem when they don't start is they "flood" out trying, ie, too much fuel. Once liquid in the cylinders, it's over the UFL and won't burn. So you have to let set and I like to take the plugs out and clean and dry them. So if the carbs not been touched, it could be dumping gas.
I'll give my standard speech, you check each system out first thoroughly, then when everything is right, move to starting.
Jumping in and not starting, you don't know what the problem is. Had each system been thoroughly checked, that is eliminated. More likely to fire right off. Work methodically.

Proper tool for the job is always the best approach.
Jumper cables are made to jump start cars with low batteries.
Grounding straps are made to use for grounding.

if you want to cut up the cable to get a section of cable to make a strap via end clips that's your call. Again a local hardware would have large gauge wire to adapt. Frankly, for the few bucks I'd go to the part store for a ground strap and keep the cables in tact. Sell them, if not needed.

Also, investigate why you think it needs additional grounding as there maybe other issues to resolve.