stock upgrade possible?

I'd say rebuild High performance stock. Look at firm feel's site. Use moog parts and add a front sway bar. Buy the Borgeson power steering box and 76 Cordoba pinned calipers and brackets. Use the larger tie rod ends and adjusters. add a set of Bilsteins or KYB's. You wouldn't believe the difference.

Basically, these aftermarket firms are pushing you to buy a brand new suspension just to replace your worn-out service parts. New bushings, ball joints, tie-rod ends and shocks, to factory HD standards, would make a world of difference. HD torsion bars and rear springs, and any of the available front/rear antisway bar setups (even the cheapie Addco) would basically give you new car handling, if combined with updated alignment specs and quality radial tires.

Be real -- are you prepping to run the Silver State Challenge? Do you regularly autocross or road race? Don't get conned into a full-on Pro Touring conversion unless that's what you have your heart set on. If so, be prepared to spend money.