3rd gen rear chunk help!

I have a 87 firebird w/ a 10 bolt non-posi rear. I want to try to
put a 78' firebird posi chunk (it is the lighter duty non clutch type). The 78 chunk is the higher gear ratio type, I believe the chunk changes after 3:08 gear ratio right? anyway I don't want to waste my time so does anyone know if it will interchange?

somebody correct me if I am wrong...but You cannot use a 2nd gen rear in a 3rd gen without some serious mods...

I cann tell you that s-10 trucks and Blazers are fully inter changable....

BUT... with all 7.5 ring gear their is 2 different types... for the actual gear assembly (ring and pinion... so If you get one make sure you have the chunk!

hope that helps