Wheel hop in REVERSE?

Are you certain it's actually wheel hop? Or could it be the clutch chattering? In the early 80's my neighbor had a Ford van he put a new clutch in and it did it in forward only. Wish I could remember how he solved it. Think he replaced everything second go around but that's been 35 yrs so the memory is faint.

If it is actually wheel hopping that easy it almost has to be a problem with the drastic pinion angle you described. I've never had a problem getting the trans output shaft to zero, except in one custom install I inherited. Does it have the correct motor mounts on it? If the engine is up too high that'll lower the output shaft angle