Now if you were talking the original G3's (the beige ones) they were ATX and didn't have those freaky connectors. That was nice, especially when all it took was a jumper that moved it from Mac to PC(ATX).
What board are you working with?
If that's the case, I need to be ordering yet another beige G3 logic board (I used NexComp, for what I've got on the way already), and a 300W-320W ATX PSU from NewEgg! Then all I have to do is, retrieve my old AIO G3 case from my storage unit, go to Lowes for a sheet of 1/2" white birch plywood, and by the time I'm done I'll have an AIO G3 that resembles a vintage television/stereo console!
Along with the above, I'll be resurrecting my G3 MT (with the parts mentioned above from NexComp), resurrecting my late mom's Performa 637CD (new battery) and building 2 Wintel boxes (please don't ask about this one ). And, I'm planning to buy me a Mac mini, sometime this summer, and mod it as soon as I figure out what it should resemble. I haven't had this much fun, in 1 year, since I did my very first Mac upgrade, in sticking a COMM slot ethernet card into mom's Performa...WOO HOO!!