Yeah, i've read that the rearend steer that is common to mustangs is a result of the soft stock rubber control arm bushings even if the bushings are fine. The wheel hop is likely a result of the shot bushings, my car also does the "sway" but my bushings aren't cracked or anything, just soft. If you replace at least the bushings with polyeurethane ones, or get aftermarket control arms, it's likely the problem will go away. good luck.
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'84 Mustang 5.0 LX
My car