what causes BAD wheel hop in reverse

This is actually pretty common, I've even seen it in bone stock trucks when trying to backup a load or a trailer. Part of the problem is the springs are made to work in the forward direction, not the reverse. Yes the pinion is going to point down in reverse, up in the forward position. The fix Chrysler had for some of these was to adjust the pinion angle with wedged shims under the spring perches but that's probably not all of your problem, You need new springs and then adjust the pinion angle for approx. 2 -4 degrees nose down with the weight on the vehicle.

Other than that I guess you could put traction bars on it backwards. :)