i have a 71 dart with a limited slip diff in it i would like an 8 3/4 but cant afford one what rearend does this car have and where can i find gears for it btw its a dirt track car

 

if you post a pic of the rear, we should be able to identify it for you

 

In the chart below, your possibilities are one of the top two

(You evidently don't have an 8 3/4, the only axle with a third member, and Mopar did not use the bottom two in your car)

 

If you have a LS then it's probably going to be the 8.25 rear axle. Most places will have gears for it. While you have it apart, inspect the clutches in the LS and replace them if they look worn. No point in going in there twice.