i have a chance to get some 3:42's from a friend out of his 89 Rs(2.8 5speed,120,000?) would it be worth it or should i get a brand to set? it would be pretty cheap to get them from him, im guessing around 20-30$$

I would be putting them in a 87 TA 305 TPI, stock gears are 2:73(think)

also would they mess up my limited slip or no? his is one wheel wonder

 

Seems to me most 87 T/As have the 9-bolt, in which case they won't work at all.

But, you might have a 10-bolt. In that case, they won't go on your carrier. You'll need to come up with a 3 series carrier in order to use them.

Other than that, I don't see why not.

 

k, im a little new to rearends, but if i got the complete thing from him, case and stuff, would i be able to take out the internnals of his and put mine in,minus gears?

 

There is nothing wrong with used. Just pay attention to the contact pattern BEFORE he pulls them out of his car, so that you can set it up the same way in yours. Sometimes they are not a direct swap, due to housing varients, it may need a depth change. Just think, with a used set, theres no break in period....you can go hammer it when your done with the swap.