I think the main problem is that 2nd gens use leaf springs and 3rd gens use coil springs. If your truck has a 78 Camaro clip, it should be made for leaf springs though? Is there something I misunderstand about your set up?
the rear end i have now is a 3th gen camaro but i want to put a 2 gen camaro rear end in the truck . my main question is can i swap out the disk break from the 3th gen rear end to the 2 gen rear end