my block is at a machine shop and they just called me and said the main caps i gave them aren't right. My block is from an 87 and had "YYY" castings in the lifter valley, the main caps i gave them were from the block i took all the internals out of, which was an 86, though i don't think the block was 86, but i wouldn't know. the motor the caps are out of was rebuilt and had all HO components, E7 heads and HO intake and such. the castings on that block was "XXX". are the main caps really different, or do the guys at the machine shop not know what they're talking about? HELP PLEASE!