My O2's worth.
Pro's:
- 3400# with driver is a nice race weight to start with.
- TH400 trans will live forever in a 650 fwhp application. And if you fully rollerize it, the hp loss will be minimal. I highly recommend having roller bearings installed throughout the trans if you go this route. Also, it is beneficial to have the 1st and 2nd gear ratios changed to be as close as possible to the TH200 trans' 1st and 2nd gear. (TH200-4R first = 2.74, second = 1.57 vs TH400 first = 2.48, second = 1.48) This will dramatically help keep the engine in it's power band.
- A properly built 8.5" 10 bolt rear end will take you a very long way and be every bit as strong as other differentials. Not to mention less hp loss to turn it. Just ask those who have taken them deep into the low nines, some out there who have even gone high 8's with a purpose built 8.5" 10 bolt factory rear end.
- Low impedance injectors are not needed with todays technology, if your goals are mid - high 10's. As said before Mototron 60# high impedance injectors can safely support 720 fwhp, with a matching fuel pump and properly sized lines. Combined with a Turbotweak chip, you're good to go. If you are more comfortable with a larger injector, then go with the new 80# high impedance injectors. Just know that drive ability will be slightly lower with the larger injectors. MPG and street manners etc etc etc. Turbotweak does have the chips for these 80# injectors though.
Con's:
- Changing rear gear ratio much higher than a 3.73 will move you out of your effective power band of a stock cam, stock headed engine. Sure it will help the car react and accelerate a little bit quicker, but it will cost you drive ability on the street, especially with a 3spd trans and no overdrive or lock up converter. 3.42's are very well matched to our stock motor's torque curve with a TH200-4R trans' gear ratios. We're talking maybe 1200-1600 rpm worth of power band here to work with on stock engine parts. 3200-4800 rpm realistically.
- Suspension will definitely need to be addressed if you want to hook the car hard enough on drag radials with a trans brake to run high 10's. This is where a nice set of heads and a roller cam will pay off big time. Ex: A stock motor typically needs high boost launches and 1.50ish short times to run in the high 10's with a stock long block, vs moderate boost launches and slower short times to reach the same goals on a heads, cam and intake motor. It's always better to run lower boost on these motors from a reliability stand point.
If I were to spec a turbo for this combination today, taking into account the car, street vs strip manners and your goals, I would choose a Billet 6265 air cooled dual ball bearing turbo with a SP compressor cover, a .63 A/R 3-bolt turbine housing and a heavy duty wastegate actuator. This turbo would definitely support high 10's at your race weight and have the capability to go faster if you went with ported heads, matching intake and cam. I would also contact Dusty about a PTC converter for whichever transmission you go with.
Hope some of this helps and sorry so long winded.
Patrick