I have followed this thread with some interest as I installed a 1.9 AMC
head (back when they were still available) on my '84 7 passenger right
out of the box.  That was in 2001.  So far it hasn't come apart and I
haven't removed the head for inspection.

That said, when Boston Bob built the 2.1 for my '85 he used TRW valves
in AMC heads.  In our discussions, he said that the real problem was
with the keepers on the supplied valves and that with reworking the
keepers the supplied valves were "OK" but TRW is better.

Mike
Houlton, ME