If you keep the Saleen watts link just replace the bolts.
For the center pivot bolt and the link bars to pivot bolts I replaced them with grade 12.9 Allen bolts from
www.belmetric.com. They are m14 x 2.0 x 60. Part # 14C60D122P. The center bolt has to be ground down a little to about 55mm because the diff cover hole isn't deep enough.
The link to frame bracket bolts are a little longer: m14 x 2.0 x 80, part # 14C80D122PPK.
Bel-metric offers the associated hardened washers and lock nuts too.
I'd also replace the set screws with brass tipped stainless hex socket screws. They are available from Buckley QC Fasteners 800-344-3874. They are m5 x 0.8 x 10