I will be doing a similar build. I decided to use the 1954 "oval exhaust port" heads. They will flow well. I will also use one of my 1954 4 bbl intake manifolds. This prevents cooling system issues, and also having to run the 1955 up camshaft. I don't want to build a expensive Frankenstein, so I am taking a smarter yet simpler approach. My cragar adapter is for the Caddy LaSalle 3 speed. I bought a 1937 top shift transmission, I am going to machine it to accept the later 1940's internal gears/shafts so I don't hurt it with my Hemi.
Note: I am thinking of doing a second build, and machining a adapter for a real transmission (A833 Mopar). Everyone seemed to make adapters for weak transmissions back in the day, and currently for that matter. But a mild build should work in my case with the Caddy trans.... It's sacriledge I know, but it's the only piece of GM junk that I could find that would keep it simple, and put the shifter up close to the original location of my 34 Plymouth Coupe.
If one of my extended bell engine blocks checks out, I will go the 354 1/8" over bore. I have a set of stock 354 rods and pistons that I can use.
I have later blocks, but see nothing wrong with the extended bell set up. I prefer manual transmission set ups anyway...
Please keep me posted on what you end up doing. PM me if you like. I have spent a couple of years researching and gathering parts for my set up...