The Rear Bumper swaps over directly. Not the front bumper though, they're mounted differently. The 1st Gen Bumper is a little shorter (center section) and not quite as tall.

I have a Chrome 1st Gen Bumper with 2nd Gen Bumper Corners on my '87 though, it takes some modifications to fit. Mine was sliced to fit a snow plow frame (bumper is mounted to the plow frame)