Thanks, everyone for the advice!
I had originally thought about putting the 350mhz card into one of the 300s, generally assuming the 300 would have taxed the motherboard (neglibly) less. I will take a look at part numbers, just so I know what I have but I'll be leaving the 350 on the board it came with.
As for the case swap... I'm not really a fan of the G4 cases... It might be an easier swap, it just has no appeal for me.