rear axle question, hope you can help.

[59weasel]

ok, not sure if i should post here or the suspension section but here goes.
the camaro subframe is in, (glad that is finally checked off the list!)
but now it's on to the rear. i was told the rear is out of the same year of camaro or possible that it could be el camino. 1st. question is how do i find out which, and is one better than the other? 2nd. question is what "OTHER" axle is going to be close in size but same bolt pattern, and strong? i'm running a 454 and 700r4. and a four link and bags. i'm not dragging this but i don't want to rip it apart the first time some kid pulls up and thinks he's got it easy on me! thanks for any and all ideas, or whatever you guys have had or delt with. (good or bad)