Gearing Advice for 2800lb car

[Lowfast]

I know there are a number of threads about gearing of which I have searched and read. My question has a slight twist. I am working on a ProTouring 1965 Ford Falcon and have the drive train out of a 06 GT that will be going in it. I have the stock 3650 tranny and will be running an explorer rear-end that currently has 3.73 gearing. The plan is to stay NA with stage two heads, aggressive cams, FRPP/JPC intake, long tubes yada yada yada... The goal is to hit as close to 400rwhp as possible. Given that the car will only weigh about 2800lbs with me in it what would be the ideal rear gearing for a stout N/A combo? Stick with the 3.73's or go to 4.10's Rear tires are 25.5” o.d. (315/30/18’s) The car will be for street cruising, autocross and some open track, might hit the 1/4 once or twice just to see what it can do. Is the appropriate gearing affected by the low weight? Or is the weight arbitrary and the engine/tranny dictates?

Opinions welcome.

 

[BAKnBLK2010]

I think the 3.73's would be perfect for your combo if you really aren't making it a drag car. For drag racing you would need the 4.10's or the 4.56's to get the most out of it.

 

[stkjock]

3.73s with a 25.5" tire should be fine. it'll let you hit about 130 in 4th at 6500 or so.

 

[gil_t2]

It has more to do with your tire size, and the trans gearing. The 3650 trans has a 3.38 to 1 first gear, if you are using a 25.5 tire i would use 3:55 or 3:73

 

[Lowfast]

Thanks for the help! I will stick with the 3.73 that I already have. With upgraded valvetrain is it safe to up the shift point to 7k on an N/A engine or would this put me on borrowed time?

 

[stkjock]

stock short block - you'd probably be ok, just don't miss a shift

however best to get it on a dyno just to see where you stop making power, you may not want to shift it so high

 

[Lowfast]

Probably would not regularly shift there, but sometimes on a track if you can wring it out an extra couple hundred RPM it saves shifting up only to downshift a split second later. Hear you on the powerband. Hopefully with stage II heads, matched cams and FRPP manifold it will not fall flat ont he top end. One day when funds allow I would like to go built bottom-end, high comp and 8000rpm, but that is only a dream right now.