The reason why older blocks generally have thicker cylinder walls isn't to improve the quality of the product, or permit more rebuilds.
It was to reduce the number of blocks that must be scrapped because of bore location errors.
Some 3.500" blocks will allow .125" over (very accurate casting) with no bad results, some will crack in service at .090" (bore isn't centered in the casting).
IMHO +.060" is both efficient and harmless.
