From elswhere, and confirmed by posts from Charles in other posts. Quoted text- "have mounted many PTO's from early style transmissions to NP 420's and have had no problems. And a few from late to early as well. The difference is in the drive gear for the PTO where it mates to the cluster gear....

There is no difference between late and early PTO. The parts manuals state fitment to M37 ww and M37B1 ww.
PTO is only different for Acme Trans on CDN truck. (And worth it's weight in silver )
Housing and gear part numbers are the same 1954 and 1972.

Those are for the jack. It has a spud that fits the casting in the spring plate.

That's it. That is the blank off cover.

Looks like it was discontinued in production in 1952.
http://www.g741.org/ProductionChanges1.html

The connector is still current production. And, knowing the part breakdown makes them cheap and easy to source on fleabay.
I however, bought 3 pin connector and sockets so I could feed 12, 24 and GND. through it. This way, I could use standard auto stuff also .

It is held with those u shaped hooks in 3 locations and mine also has the spring clamps for the 3 wire Douglas connectors holding them.

I've never been successful in uploading here. The size restriction is too small and I don't have a way to reduce the files from my phone. (My only Internet device)

What year truck? On my 53 there is the hole with 4 mounting holes covered by a blockoff plate. They may have omitted it at some point.

The headbolts extend into the water jacket. You need to use a suitable sealant on the threads. (P2 is suitable)

It's only crazy to buy a 70 year old vehicle and expect it to be like a new vehicle. Our term for the lack of amenities is "Embrace the suck". I've hotrodded some vehicles to death. (1925 T C cab, 1926 T roadster pickup, 1971Camaro.) And driven/owned many dozens of T's A's and other old ca...

Well, there are no intake seats per se. So you can grind them in position with a seat grinder The exhaust CAN be done insitu, but you will need the necessary tools and skills to do so. Not very common anymore.

There are supposed to be 2 threaded inserts in the body. Not only for the mirror, but also to hold the deep water fording intake pipe.

I got mine from VPW. If no one here has any spare.