Howdy,
Try here perhaps:
Parts and Accessories for Corvettes. Corvette Parts for all models including C8, C7, C6 and C5 cars, plus Z06, Z51, Grand Sport and ZR1 trims.
www.westcoastcorvette.com
Alternate with no doubt, a somewhat stiffer ride:
Check out the deal on Corvette C5 & C6 Front & C6 Rear Leaf Spring Height Adjuster (Not C5 Rear) at Lingenfelter Performance Engineering
www.lingenfelter.com
I wouldn't be too concerned about front / rear & model / year. It's a bolt and it's adjustable.
Sure hope the bushing in the leaf spring isn't too mangled - I did the rears on mine and both bolts were seized and spun the bushings -which- by the way, are just glued in with epoxy. If yours do spin out, free them from what remains of the bolt, clean up the bore and epoxy 'em back in place. It's yet another faulted design on the XLR as the bushing height is lower than that of the spring so that means it's bound to accumulate water and other shtuff.
There's a flimsy locking washer on the top (paper thin) and in my case, well I replaced the bushings completely with home-made that rise higher than the spring and accept a real nut (custom). Soooo, a real nut and a washer would be a more tidy fix, just goop that pocket on top of the bushing with a good grease to fend off the guaranteed accumulation.
HTH!