Did aan engine and transmission swap on my sons '48 chev truck this past summer. Same body style. He had a chev 235 with three on the tree. We put in a Chev 250 with 700R4 auto trans. Very good combination but I would not do it again. The 250 was an easy fit and he insisted the the under hood "look" era. The 700R4 has created some problems and if I had it to do over I would have used a 350 turbo. Or would have talked him into a 5 speed manual. The auto was to satisfy his wife and two teenage daughters - so they could drive it. go figure.
All the steering was rebuilt and the brakes now have 15" Disc on the front and 15" drums on the rear. The rear end is actually from a '99 Chev Blazer.
