I have a 350 in a 58. I use a TH350 and it works well with 3.08 gears. I assume you plan to change the rear end. My 58 had 3.90 gears original. Running a 400 transmision and the old rear end causes the gears to be turning much faster and may fail due to high revs. Lots of options for rear ends that have higher gears.
