i'm due for a rear end rebuild in the '86.looking at 3.42 or 3.73gears and a posi diff.the thing is i've got the venerable 7.5"open 2.73 slug.is there another rear that is stronger that would be an easy swap for this car?or would a rebuild with good parts handle 400-420 hp?

Strange Engineering, Moser engineering and Currie Enterprises make bolt in 9" Ford and 12 bolt Chevy rear ends for the 3rd gen Camaro. They aren't cheap, but they are strong. I don't know if the 7.5 will handle over 400 HP consistantly or not. They hold up pretty well on street tires, but traction may break it. If you decide to try it I would use a new Eaton 28 spline posi, Moser axles, a T/A cover, a good installation kit with Timken bearings and good 7 5/8 gears.