This combo was kinda thrown together on the cheap and I know can be improved on but I’m curious from guys that have been down this road already.

Stock 6.0 with 317’s with valve springs
Sloppy best cam 219/225 .595 lift
Stock Ls1 intake
Cast ON3 78/75 with 3” exhaust
1000cc injectors with flex sensor
T56
9” with 4.10’s

Now, I’m thinking of dropping down to 3.50 gears.

 

100%, get lower (numerical) gears. I have 4.30s in my Formula and it's not able to build much boost at all in 1st and 2nd gear, not to mention I'm shifting out of 1st at like 25 MPH. I'm probably going to install 3.54's this winter. If it were my build, I'd add compression, since you run E85. I'm at 10.5:1 in my 5.3. But you can make up for that with more boost in some cases. If your turbo has a 3" outlet, I'd see if you can step up to a larger A/R housing with a 4" outlet. Seeing that you're 6 liters, that single 3" can choke you. I have a 1.25 A/R Gen 2.5 VS Racing 78/75 billet on mine with a 4" dump, and it's not lazy at all.

 

I’m gonna get rid of the spool in favor of some kind of posi along with probably a 3.50 gear. I know a next gen 78/75 is worth about 100hp, a better cathedral intake would help and so would heads.

 

Have you maxed this combo out?

 

Not yet

 

Street car on hard tires?

 

Street car on 315’s street tires.

 

I'd drop down in gear.

Adding engine compression would be on my list, better ported heads would add.

 

You already have the potential to make enough torque to eventually destroy the t56, so that would be my suggestion for an upgrade. If you change out the 4.10's and street tires you will be putting a lot more stress on the transmission. As it is you will never hook enough power to hurt it, but when you get tired of highway speed burnouts it will have an expiration date.