first off I have an automatic transmition (sucks, but the car was a great deal!) when people have done the auto to manual swap, they had an option to keep the 3.909 gearing. If I took a 4.10 n/a rearend off a junked 7, would it work with the automatic's driveshaft?

 

I'm implying I would be using the automatic transmition also

 

if you swap trannys, you'll need to swap drive shafts.

If you want the 4.1 rear end yes you can swap it in, but you may find you like the 3.9