Yup just the normal push on style.

I don't remember the size though. Check with a caliper and buy accordingly.

Yes. Just measure the free space over the valves and make sure it has not been milled to death in the past.

Had to just discard a 327 head that had been milled down until the combustion chambers looked like the paw prints of a light weight mammal. That was with the parts of a car with a brake drum turned a quarter inch oversize.

Quote:

so just speed nuts then? I have access to the backsides of all the panels that it shouldnt be a problem

My head has 14 mm plugs. It has 2 cylinder inserts, 1 actually broke off 1/2 way in.
My head has 14 mm plugs. I have another head with 10 mm plugs. My block has the letters CE stamped on side of block.
I would like to use the new head with 10 mm plugs.
Will this be okay?

The meter connected to the BAT terminal at regulator will be on all the time and I suppose that is OK as the constant drain is probably quite low -- certainly far less than most modern cars.

Connected to ign sw GA terminal is also fairly accurate because its power originates at the same BAT terminal on starter solenoid so has the same number of wire terminal connections. Route does have one splice plus the ign switch as possible additional places there could be loss.

Cleaning the wire terminal connections and allowing the 1/10v for any ign switch loss would probably work just as well. It would also allow you to monitor any heat related issues in switch as well as be able to turn everything off.

Probably the two worst condition Packards currently for sale:

https://www.facebook.com/marketplace/item/526208629603299/?mibextid=dXMIcH

https://www.classicautomall.com/vehicles/4570/1955-packard-patrician-sedan

Looks like a decent project for not even 2 grand

https://www.facebook.com/marketplace/item/289087970682079/?mibextid=dXMIcH

Thanks Howard, I went for a drive just now, and actually am happy with the numbers I measured. The first few minutes of driving at speed, I was getting 7.3 to 7.4, and after about 15-20 min of driving I was getting about 7.1 to 7.2. I have the gauge pulling a voltage from the back of the ignition switch, so there might be a 1/10 of a volt or so getting lost along the way.
I guess the best place to hook this gauge would be to a ground in the engine bay, and the bat terminal on the voltage regulator....That would give me the most accurate reading so I can really be sure if the 7.4 is being maintained. I may optimize the wiring and take some more measurements, but the voltage is in the right ball park.

I saw some come to auction this summer, some large parts collection. I almost bid myself, but got enough clutter, lack of motivation, and pickup was too far. One of those I shoulda bought all the lots, but it was already in multiple storage units, so even the owner didn't have enough space and monthly fees accumulate faster than value. Once it's gone...
Ebay is a bit chaotic/hit and miss. You should plug into the auction network(s). I use proxy-bid.
Since aluminum, also have to check it thoroughly that it's still good. Won't see on a internet photo. Can repair cast aluminum if not too badly corroded. Never seen any numbers made, but doubt there were that many ever made, especially 4 P which was low production/not hotrod favorable.
The attrition rate may also be high. Period hot rod parts is a narrow niche, hoarded by period old timers. CA would be the place to search. Hot rod culture was hot and home there in the day. They have large parts swop meets regularly at some venues. East coast, Hershey / Carlisle twice a year but AACA mostly. There's a guy on here that hawks parts, ask him to be on look out.
It's even happening to modern vehicles. My friend needs a trim part for his foreign car that's obsolete. It's even harder to track those import parts. Internet has no update. Searching past posts often vapor.