My car is a 70 Challenger, 340 powered and 5 speed. It had new rubber lower control arm bushings, offset bushing in the uppers. Also, the car has Koni shocks all around, with 1 inch torsion bars, and FirmFeel stage 3 box with fast ratio pitmen and idler arms. It has a Hellwig sway bar in the front and an Addco in the back. It has 245.45r17 tires all around. When I redid the car I welded in sub frame connectors and torque boxes.
The car has around 4k miles on it, in its current form. It had the standard +3 caster, -1 camber, and 1/8 toe alignment. The car cornered ok, but the steering had a lot of slop in it. I would routinely drive with both hands on the wheel. Another problem was tire ware. Despite the negative camber, I was still wearing the outside corners off of the tires.
I decided to go with the Hotchkis upper control arms and replace all of the bushings with poly. I also purchased the sector shaft support kit from FirmFeel. It took all of last weekend to get the parts installed and the alignment set. The Hotchkis control arms a are a real bear to get set correctly. I had to assemble each side 3 or 4 times to get the caster/camber correct. I also had to do some minor cutting and grinding on the frame rails to get the proper clearances. On the sector support, I decided to slice and re weld the bracket to get the bearing alignment with the K frame perfect.
After getting it back together, I took it for some short drives last week. The car handles amazing. The steering is completely predictable. There is still a few degrees of movement in the steering box, but the sector support works great!
Today I put 200 miles on the car. It was a mix of I80 and twisty mountain roads. The passing lanes were a blast on the mountain roads. The rutted out concrete (from winter tire chains) wasn’t nearly as scary as it had been. And the hairpin curves were complete fun. I can’t wait to drive the car again on a less busy day!

Sounds like a funnier, glad it is working out for you. Slope in a Ff box? That does not seem very likely, as Dick and his crew always does a superb job on those boxes. I have heard of similar problems like that due to cracked/fatigued k-members. I know several members have had problems with cracked k-members and had the same problems as you were having. Take a look at it and see if maybe you have some damaged on it. Hotchkis control arms are made for ultra inner fine tunning and that is exspected of them. Tubular arms are great, but when you can tune them for better handeling performance, then the extra work and effort is well worth it.

Glad to hear you are enjoying your new upper control arms.

I felt that with the fast ratio arms, and wider lower tires, steering play was exasperated. When I redid the car I welded all of the seams on the K frame and reinforce the steering box mount. In my case, the sector support made a noticeable difference.
Changing from the rubber bushings to the poly/heim joints seem to stiffen things up quite a bit. I expect tire wear to be a lot more even. There are a bunch of speed bumps in my neighborhood. The car feels/sounds so much more solid with the new parts!