The twin turbo cards won't work in your more modern macs (not even G3s I believe, but correct me if I'm wrong). They use the apple connector and require a VGA adapter (no chance of DVI at all with these bad boys). There are also a few different Twin Turbo cards, and each EPROM revision (no telling what you'll get) requires a slightly different hack. Plus you have to know your monitors' modelines and do some math, and then tweak and tweak to get it as good as it'll get, with the end result not being as good as a simple $15 nvidia card in a G3/G4.
^^^ all of that is why I didn't bother. I do this because I fell in love with System 7. You'd have to have the exact same card model + EPROM revision, plus have a 9600 in the first place which is mandatory (the driver is specifically for 9600s)