hm when i was driving w/ mouse i used this setup:
mouse to steer
lmb: shift up
rmb: shift down
scroll button pressed: pit limiter
w: acclerate
s: brake
q: look left
e: look right
c: clutch
space: handbrake
arrow down: look back (never used it anyways)
been driving this almost 1 year and reached top almost down to wr on some combos
but now a got the wheel, its much more comfortable. since i was taking part in GTAL and had some endurance races, i sometimes suffered from major fingertip pain because of pressing w/s for accelerating/braking for hours.