PCI-e and PCI risers/adaptors/problems

The situation:

I've got a current generation Mac Pro (intel quad core if that matters -- but I doubt it) and a National Insturment's Digital I/O card which is proudly says "Mac OS compatible" yet a PCI card.

The problem being Apple hasn't used PCI mobos in Mac Pros in what 4 years?


Question:

Do they make a pci-express riser/adaptor that will allow a PCI card to be connected? And how much of an impact will that have on timing?

Assuming I can connect it, will I run into and lower level conflicts/errors/recognition problems with the mobo and inserting a foreign object in the wrong hole.