Swapping main caps can be a bit of a crap-shoot as to whether they will really end up fitting properly or even acceptably; this even after a reasonable effort in line-bore/hone correction.
The problem is that when the blocks were originally machined by Ford, they didn't seem to really care to much as to whether the cap to block parting line actually bisected the hole through it's center, nor whether the block to cap locating registers were actually equal distances from the center either. After all, if they had done so accurately, then all of the caps could be swapped in positions on the block, or even from block to block without any concerns for ill fitment.
So..................the closer to the same production run that the substitute caps might come from, generally the better the chances that the resultant fitment might be found to be acceptable.
Scott.
