Find a later block 283 punch out the bores to 4 inches and get a 3.25 stroke crank. Bone yards are full of them down here. Friend has the the crank [forged small journal], rods, and pistons out of his 66 Impala. [dummy only had water in it when it froze a couple of winters ago, you guessed it cracked the block] He went with a 350. Has no use for the bottom end now.