I have 1984 z28 and the rear end blew up. I can Either buy a 91 rear end posi for 150$ but a guy i work with has a 70's camaro rear end also posi that hes giving away, would the 70's rear end work ( and how much fabrication) or should i just get the 91 rear end that would just bolt back in?

 

whats the gearing on the 2 axles? the 91 will be easier to install but i have no idea what it would take to put in the 70s axle (could be there both the same as far as mounting).

 

You could take a picture of each one and post it up so we may slap an eye ball on it.

 

Get the free 70's rearend and sell it.
Yours has coil springs, and is mounted to the car by control arms.
The 70's rearend has mounts for leaf springs, and no provision for the torque arm mount. So you would have to cut all the control arm and coil spring brackets off your existing rearend, weld them to the new one, buy or fabricate some kind of mount for the torque arm. I'm also sure there's a width difference between them (have to look up), so your wheel backspacing may have to change. Other than that, it's a simple bolt in procedure!
EDIT: it's looking like the rearends are close in width, maybe within 1/2" of each other. 2nd gen is 62.5" overall, getting varied numbers on the 3rd gen. So, if anything, width should be the least of your worries.

 

alright il just go for the 91 rearend then, thanks alot guys. i may pick up the 70's and i suppose try to resell it.

 

For a 70's vintage posi rearend, free is one heck of a good price!

 

Thanks alot guys picked up the 91 posi, putting it in through the night haha

 

Well 84 how did the install go?