Which longacre for bump steer

E-body! Well that would have been good to know. Yes it has the taller spindles because it's an E-body, but E-bodies had different geometry to begin with so it's not like those spindles add any bump steer on that car, it was designed for them.

Changing the alignment does change the bumpsteer, but that still may not be what you're feeling. I run my '72 Challenger with the later FMJ spindles, Hotchkis UCA's, 1.12" torsion bars, Bilstein shocks, and 275/40/17's on 17x9's up front, 5" backspace (0 offset). Unlike on an A-body you don't need to massively increase the offset to run wider tires, so there's less of an effect there. I was running my car with -.9* camber, +5* caster, and 1/16" toe in with all new bushings. I was running it without sway bars, that's been remedied but the car isn't back on the road yet. I didn't feel like there was a ton of bump steer on that car, although the Hotchkis UCA's do change the geometry.

Wider tires do tend to track bumps and grooves more than narrower tires. The wider you make them the more they'll track ruts and bumps. I'd bet this is a large part of what you're feeling. This can be be dealt with by increasing the positive caster, which will recenter the wheels faster. With power steering I would run at least +5* caster, more if you can get it. Like anything else with a torsion bar set up the ride height plays a part too. So, what I would say is that it's probably worth checking the bump steer to see what you have. I wouldn't be surprised if you don't find a whole lot, but if it is there then you can make adjustments.

Lastly, I would remove those CAP uca's and throw them directly in the trash. That's a disaster waiting to happen. I used to run CAP uca's and lca's on my Challenger. I had a weld fail on the lca's, just like many other people that had issues with CAP's welding. I didn't break the UCA's, but there's no way in hell I'd run them again.