I put a Dana 45 from a 58 GMC in mine. Straight swap and 3.07 gears. Made a big difference.
I have the same rear in my '56 with a 350/400. That is a great ratio for that set-up but if you are running a stock 6, that is too high. That is my opinion based on experience with my 248/SM219/3.90 gears. I think there would be a lot of downshifting to second with a 235 and 3.07s.