I think the major differences will be the earlier '62 block will only be the 2 bolt motor mounts so be sure your mounts will work with that or can be adapted. Also the '62 used a cam with a thrust button, you should change that to the '63 & later thrust plate which just involves drilling and tapping the block for the 2 bolts. Also I don't know if the early blocks have the boss on the front for the alternator mount, take a look at that. I believe there was a slight change in the length of the head bolts, but not sure of when that changed. Early bolts were a tiny bit shorter, so be sure if you use the later bolts they don't bottom out in the block. There was also a difference in the thrust bearing on the mains around that time. I believe you need either a bearing set for the early block or to machine where the thrust bearing goes to use the later bearings. All I can think of right now, maybe someone can add if I missed anything.
