hi i was wondering what year and make rears will fit under my 69 chevelle. i found a 68 le mans ,and a 68 impala ,and a 73 elcomino, in a salvage yard and dont know that much about rears.
any help would be greatly appreciated this is my first car. and the engine is already done.

Any rearend from 68-72 A body will fit, also 64-66 will also but are a little narrower. So the lemans will work.

68-72 Buick Skylark, Pontiac Lemans or Grad Prix, Olds Cutlass, Chevy Monte Carlo or Chevelle and Elcamino

The 68 Lemans is the closest, but it's probably a corporate rear end. Chevy rear ends were a breed of their own. The Lemans rear will bolt right in and all the extermnal dimensions are the same, but there are some internal differences between it and a Chevy rear end.
If you're lucky, it's an 8.5 inch ten bolt, which is almost as strong as a twelve bolt. But, I'd have to see a picture of the back of the housing to make that call.

The other two rear ends, they just won't work at all.