4.10s == New Rear End?

I'm not sure of anyone that sells a complete kit with axles, diff, and gears. But I know you can usually buy all the stuff in one place. Check out www.gefracing.com
They have

31 spline axles - $225
31 Spline T Lok - $239
SVO axle girdle/diff cover - $174 you can find cheaper.
FRPP 4.10's - $180 - you can find them cheaper
Complete rear end rebuild kit - $110

If you aren't going to run sticky tires on the track, don't worry about upgrading the splines. Rebuilding the other parts isn't a bad idea while you are in there though.

1. you don't need a New rearend. Just parts.
2. Check online, local shops, and the mustang mags for a complete rearend upgrade alto of times you can get a full kit, axles, bearing, diff, and gears in one swoop.
3. If your a budget shopper and don't mind getting a lil dirty. You can pick up a used 31 spline tloc at junkyards or online pricing varies from 50 bucks- 150 bucks it seems. Then I'd suggest getting a tloc rebuild too. You can order 31 spline axles then and a master bearing kit and gears and call it done. For axles I really like Moser have never had an issue with any of their products.
But if your going to be on street tires and on the street NA odds are you won't break the stock stuff. But if a Power adder, slicks, extra sticky tires, drag strip or hardcore street racing action, if any of those are in your future yeah I'd do it now and not worry about it. Of course if your staying NA and don't do highspeed runs you might want to think about 4.30's instead. But 4.10's are great on the street in a daily driver too.