If you rebuild it is no big deal to shim the rods just takes time, one look will tell you if you can shim without repourng the babbit, and mains have inserts at least my 51 did a 216 came in it, original is original
. Get a chevrolet service manual for your year ,I found one on ebay $20 there is no end to the decision you have to make, good luck on all your decisions . smile

Bill 1951 3/4 ton 5 window pick up
1955 GMC 1/2 ton longbed automatic