It seems to me that tuning cars for the standard race tracks in Forza is relatively straightforward: Depending on your needs and your base car, optimize for various parameters. (For me, weight reduction is always a favorite -- relatively cheap and massive performance gains.)

But when dealing with drag racing, it's a whole different ballgame. For one, most drag racing fans who've played Forza (myself included) tend to be a bit disillusioned with the drag mode. It seems like AWD always has a crazy advantage. It seems like there's no way to build an American muscle car (Buick GNX, Pontiac Trans-Am, etc) to be a 9-second car. There's definitely no way to put really beefy tires on the back and lower their pressure enough to carry the front wheels. (Admit it, that does look cool, even if it doesn't always help your 1/4 mile time!)

My friends and I are looking for tips in this department. I built one friend a Trans-Am dragster, and another a GNX. I myself rock a Datsun because it seemed to own the leaderboards. 

We've optimized all the parts already (my Datsun is an R3/792, the Trans-Am is an R3/721 and the GNX is an R3/728). Now we're looking for tuning setups. We've played with gearing, suspension, tire pressure, etc., but we all feel woefully ill-equipped to actually know what we're doing. 

Any advice on tuning setups, notably for those three cars? Yes, I know I can buy setups on the marketplace, but I'd rather actually learn something and know what I'm doing. Plus the good Datsun setups are all like 50,000 credits, and I need those credits to make sure I have cars that qualify for every race! (I still haven't done all of the events, nor have I even bothered with much of season play ... )