Originally Posted by
crusty shadow
you need to forget about the camshaft, all the valvetrain hardware- those parts are not the concern. they will be machined to a specific specified size at the factory- for all intents and purposes you need to consider them exact copies of an original part.
cylinder heads along with all other parts that are cast will have production variances due to the casting process. those parts are cast in a mold made of sand. a worker takes a "plug" and then assembles that by hand and packs sand around it in the casting box. things like core shift, which worker was assembling molds that day etc will all affect the final dimensions of the part. things like lifter bores, spring pockets, cam towers will all have variances in dimensions due to those factors during the casting process. you need to consider a cast part a copy of a copy of a copy.
the longer the production run goes on the more variances there will be you have to consider each cylinder head as unique as a fingerprint. none of them are dimensionally the same the cam journals on the head may be in the same places, but the cast part of the head that they are machined out of will have subtle variances. one cam tower might be a couple thousandths taller than the one next to it, or slightly wider or slightly shorter etc. the line honing process is the only way to ensure those journal surfaces are perfectly in line with each other.
if those cam caps from a different head do happen to work then you messed up by not buying a lottery ticket instead because you got god damn lucky.