Rear end for LS-1
Rear end for LS-1 
To add to what cbrodine said, you will need the tire height and RPM you want at a given speed. The best thing to do is figure out what wheels and tires you are going to run, your driving style and purpose, then throw it all in a gear calculator and determine what works best for your needs. If you are going for cross country cruises the ratio will differ from a street / strip drag car which will differ from an autocross car which will differ from a T-Bucket... you get the idea.
Summit is one place that has a gear calculator that allows you to chose what you have and solve for what you don't.
Summit is one place that has a gear calculator that allows you to chose what you have and solve for what you don't.
If you're running fairly standard tire sizes, you might start with what was behind the factory LS1/T56. Gm put gears around 3.42-3.7. Your car weighs a bit more, so between 3.7-4.11.
I'm running an LS1 with a T56 in my 1964 chevelle. I have a 31" tall tire with 4.11 gears and it's a nice setup. With a shorter tire it would be even better actually. Right now I'm doing about 75mph at 1600 rpm in 6th.
I would suggest mid 3.x to high 3.90.. that should be a good all round great set with most common tire sizes. It should get you some good MPG..
What rear end housing to you have ?
I have 4.11's w/275-40-17 and get 26mph, runs high 13's and do well in Autocross.
What rear end housing to you have ?
I have 4.11's w/275-40-17 and get 26mph, runs high 13's and do well in Autocross.
