[Mike C]

It will be. And turbo cars don't like a lot of gear. You will be happy with the 3.73 most likely. It may even want LESS gear than that, but the 3.7 are a good start. BUT the carrier break is at 3.73 and up on a truck 12 bolt. So if you wanted to run 3.42 that would require a different carrier.

If you want new car driving characteristics on the highway with the 4L80, the 3.42 gives you a 2.565 final drive and a overall first gear of 8.48 which may be better for the turbo. Additional load helps build more boost faster.

Everything should have a limited slip IMO. No matter how little power it makes. All I can say is learn as much as you can about the power characteristics of your motor and what the final goal is. Nothing hurts more than buying things twice.

And at those power levels, you are starting to reach the limits of the truck 12 bolt. Depending on if it is going to spend anytime with sticky tires at the strip, a custom axle housing might be a good idea. A Dana 60 with Big Ford housing ends and custom axles with 3.54 gears would be slick.

Speed costs money, how fast do you want to go as they say.