I'm definitely not a mechanic, but I have a 283 in my '61 Chevy stepside and have been quite pleased with it. The only thing I need to do is swap out transmissions. The engine has plenty of zip; the transmission has no where to go.

IMHO, if I had a better transmission my "SusieQ" '61 would take off and fly to the moon. :-)

For what it's worth, my vote is to stick with the 283.

flivver

1937 Chevy 1-1/2 ton stake bed, ??
1961 Chevy 3/4 ton stepside, 283