I've bought from Keensparts when their at swap meets with my '67 resurrection (still in progress) but I've found that I can generally get better prices with Corvette America, Ecklers & Willcox Chevrolet here in the US as long as I wait for them to run specials. Good luck!
Bought a clutch from him a few yrs ago, decent price. I seem to remember that he went to the border to pick his parts up. I can't remember which catalogs he orders from for new parts.