Well, what you have to ask yourself is what driving games do you want to play, and work around those controls...
...ie: Pole Position = 360 wheel, shifter, 1 or 2 pedals.
Champ, Super or Sprint = 360 wheel, pedal.
Off Road, Indy Heat, Badlands = 360 wheel, button, pedal.
Outrun = 270 wheel, shifter, 2 pedals.
Chase HQ = 270 wheel, shifter w/button, 2 pedals.
Spy Hunter = 270 yoke w/5 (IIRC) buttons, shifter, pedal.
Roadblasters = 270 yoke w/2 buttons, pedal..
...ect, ect.
I have a couple 360 wheels and shifters and my cab (a MAME'd upright PolePos) has a pedal so I'm gonna start by going the 360 route.
I'd like to get a Star Wars/Hydra yoke later and hack it to be 4 buttons for a 270 Spy Hunter/Roadblasters yoke/flight yoke combo controller. A CPO with that yoke, a few extra buttons, a shifter, and a pedal make ALOT of driving and flying games fully playable.
If you want a nice yoke, paigeoliver has a beautiful Roadblasters yoke and pedal that he's letting go of. It's optical, so way easy to hack and hook up.
Good luck with this project. I really want to do a cockpit console (XBOX, PS2, DC) driving cab someday myself!