replacing rear end in my 01 blazer
 

i need to replace my rear end in my 01 blazer its a 4.3 liter it has 4x4 its also's an automatic. heres my problem i paid someone to go to the local salvage yard & pick up the entire rear end i was told it would be easier to replace the rear end than mess w/the gears in the pumpkin. so anyways said mechanic took the cover off took all the gears & whatnot out & has yet 2 come back. so now im left 2 decipher with limited knowledge on which is the correct rear end to purchase. im told theres 7.5 & 8.5 i do know theres is 10 bolt pattern on cover and 28 spline i believe. can anyone throw me some advice cause im swimming here.

code is in the glove compartment.

ok ill check the glove box for
that code thank you for your help!

look at this picture

look at RPO CODES on glove box

also make sure get correct rearend from 4x4 blazer not 2wd or ZR2

because 2wd have narrower rearend and ZR2 have widen rearend.

4x2, 8-1/2" ring gear (3.42 ratio, GU6)
4x4, ZR2 opt (3.73 ratio GT4)
4x4, w/o ZR2 opt; 7-5/8" ring gear, 3.42 axle ratio (opt GU6)
4x4, w/o ZR2 opt; 7-5/8" ring gear, 3.73 ratio (opt GT4)
4x4, w/o ZR2 opt; 8-1/2" ring gear (3.42 ratio, GU6)
4x2, 7-5/8" ring gear (3.42 ratio, GU6)

if your glovebox say G80 that means u have a POSI rearend.

thank you 4 ur time