So, is the sm420 the part number for the original 1953 tranny. By the way, your 235 should easily be up to the task. I put those same 3:55 gears in my 1940 with 216, and it's been great.
Mike Burns 1940 Chev 1/2 ton 1953 Chev 1/2 ton 1950 Studebaker Starlight Coupe 1947 Indian Chief 1943 Indian 741