As I understand things, cards for the 7300, 7500, 7600, 8500, 9500 and some 8600/9600 (non-Kansas) machines will be compatible, with a couple of qualifications. First, the 7500 shipped with a 601 card, and I’m not sure that would work in, say, a 7300. I bet that it would, but never tried it. Second, most 604 and 604e cards should work across the range, but there were 604e cards that ran at 233mhz or so, which might not work in older machines because the faster processor speed demands a corresponding increase in bus speed, which the older logic board might not manage. I’ve even seen 200MHz processors cause instability in some pci Macs. Some of that could have to do with cache limitations, in particular, but I believe the faster 604e cards especially needed tuned logic boards.
Kansas machines with 604ev processors will only work in Kansas boards, which restricts them to the final 8600 and 9600 revisions.