What size is my rear differential???

Hey,

just wondering what the size is of my rear differential, i want to purchase some better gears for the back. What is a good steup? 373, 410 any input would be great.

What year is the car?? 1992 and up is 8.8, I'm not real sure of the box bodies.

1988+ are the 8.8 inch rear ends, prior to that I believe it was a 7.5"

All box bodies are 8.8 inch. I would go with 3.55 gears. I wouldent put 4.10's in, I only would if you draged raced you car ofton,or dont care about gas mileage.