Will I have mounting problems with PICMG motherboards in normal AT or ATX cases?

I've got a decent collection of SBC I'm looking to tinker with finally. I've bought them off and on from Ebay when one popped up that was interesting or cheap.

I've got 386, 486, Pentium, PII, Slot 370 PICMG boards I've bought and filed away nicely in ISA slots on old dead 486 motherboards for storage. None of them support external AGP ports sadly, but a nice fast PCI 3d video card is probably more than enough for the limited CPU power available

Some have worked fine in a Sergey Malinov ATX ISA backplane but I'd like to dip into the "real" PICMG standard with PCI support and all that.