I have a 66. I just got 5 new (to me at least) rims that the seller says are for a 60. I havn't actually tried them but the bolt distance measures to be right and the hole in the center seems to be the same size. They seem to be 'originals' since these have the clips and the ones that are currently are on my truck do not. 3 of the rims that came with my truck are 6" wide and one is 5.5" wide (measuring the bead area). These 'original' rims I just bought are 5".
So what's the standard? And are there any differences between wheels/rims from 60-66? (comparing 'like' models such as 60 C10 with 66 C10 of course) Thanks.