Big Block Suspension Question

When weight goes up, spring rates and shocks just need to be stiffer, whether coilover or torsion bar; either system will do the job.

I have 1.14" Sway-A-Way torsion bars in my Duster and it handles like a modern car. Definitely stiffer ride than stock but not harsh, it's a really nice feel. Like in the old GTX Car and Track road test on YouTube, "The suspension has a big, beefy feel that invites hard cornering." I can whip the steering wheel around at highway speeds and the car goes exactly where I point it with no loss of grip, pretty amazing tbh. Every time I go to a time-trials event people are impressed with how it handles around a tight track-day course. And I'm currently only running cheap garbage parts-store shocks and the rear leaves could be quite a bit stiffer (pro tip, Hotchkis springs are not nearly as stiff as they should be!)... quite a bit of room for improvement.