Not too surprising that you’re maxed out at +2.5* of caster, probably stock UCA’s and bushings. So that was the alignment as it was before?
/6 cars did come with smaller torsion bars than the v8 cars did. And even the V8 bars were too small, especially once you add radial tires. Now I wouldn’t recommend anything smaller than 1” torsion bars. PST makes some nice 1.03’s, they’re a forum sponsor.
Have you checked the condition of your suspension bushings, ball joints, tie rod ends etc?