My friend is upgrading his rear end in his 87 from a 12bolt 4.10 posi to a 14bolt 4.56. Just wondering, since my 97 silverado has POS 3.08 if the rear ends are interchangeable? They measure the same width and same pinion except the shock mounts look different. Are there any issues swapping a rear end from an 87 to a 97?

the bolt pattern on your rear end is metric, his is standard,looks almost identical but is just enough to make your wheels not fit. other than that it should swap as long as the spring pads are the same width.that is as long as you dont mind loosing your rear abs.