Birge,
I just did the swap you are describing. I've installed a 235 out of a '56 Bel Air into my '50 3100. The 235 originally had a Powerglide. Had a guy do the basic engine work for me and I dressed it out. The swap went much easier than I thought. Original carb had autochoke. I installed a manual carb to keep it original. My exhaust system bolted right up, no problems. All the linkage went on without a hitch. The front motor mount holes were there so no drilling. I was expecting some issues based on what I had read but easy change. And this is my first restoration.
Definitely take the 235. A bit pricy to rebuild but I had to look for a couple of months to find my 235.
