89 Accord head & head gasket oil leak

2 things in this one. Did a full rebuild on 89 accord SE-i.

1) Went to a shop and ordered a complete reman head with camshaft,
etc. First time he ordered the wrong one as there are 2 different
dist. bolt-up designs for this car. Then he got the right one and
after loading it and examining it in the parking lot I noticed that the
end cap was missing. So I went back in and told him and he proceeded
to (in front of me, no less) take the one off of my old head and give
it to me. I told him that I didn't think that was acceptable as I
thought that the head and caps, etc were line-bored so that any
inevitable minor discrepancies were uniform across the length of the
head. He basically looked at me like an a**hole with two heads and
reluctantly reordered one more time...or so he said. I now know I
stupidly left my old one there as i was all PO'd. he could have just
swapped the used cap in and resold it to me. Either way...were my
original concerns valid?

2) After finishing the same rebuild I had oil leaking at the head
gasket. I snatched it back off...30mins...nice!...replaced the gasket
figuring i goofed and had the same problem. Then i did it one more
time but this time with a shim too. Same damn leak. Ideas? Car is
gone now, but I was always curious. Block was reworked too. i just
couldn't rationalize anything to cause a leak that a gasket and a shim
couldn't compensate for.

kevin