Steering All Over the Place at 55mph+

Not sure you need to loosen the LCA adjusters. I would do one side at a time. Jack up by LCA to keep it close to ride height and remove wheel. If you left the front suspension hanging, the UCA would be tight against their bump stop. Could first support frame rail, then jack LCA up a bit, but not hold all the weight. Main thing is don't fully tighten the UCA bolts unless the car is supported by the wheel at normal ride height. That keeps the rubber bushings at the no-twist state in normal conditions. I did mine with the whole suspension apart, so might be missing something.

For those also changing the upper ball joint, remove it while UCA is installed so it is supported. Don't use a pipe wrench, like the tech did in a FantomWorks episode. There is a special socket for that ball-joint in two sizes - 1963-72 A-body and 1973+ A body and all C-body (B & E same as A?). I have both sockets. If the ball-joint threads got buggered so won't torque down, but is still tight in hole, easiest fix is to tack-weld it at 3 spots. You'll have to grind those off when you change it again in ~250K miles.