PCI vs Mac

I’ve been on a learning trend with Apple computers lately.  I’ve stayed away from Macs as much as possible (mostly just to keep from having to to tech support for the Production department) but I rebuilt a Powerbook for Marketing and after all the Drobo stuff I’m getting a hang of how to work with them. 
I had to fix one of the TimeMachine sparsebundles that got corrupted last week.  This week, I’m learning the difference between 5v PCI and 3.3v PCI cards.  Evidently, the G5 series decided to go with 3.3v which means the SCSI card for the scanner (once again, Production) won’t work in the computer they want to use as a scanning station.  5v PCI cards are long-short, 3.3v cards are short-long, and cards that can do both are short-long-short-medium.  I’m guessing they’re going to get a new scanner after it’s all figured out.