Where to buy bolt-on wheel spacers?

[newbe351]

I need a set of 1" wheel spacers (6 x 5.5") for the rear of a '66 GMC fleet side to correct a wheel back-spacing issue. A search on line provided me with a wealth of information for Toyota or newer Chevy hub-centric stuff with metric studs. I need (want) standard 7/16" lug studs so I don't have to mess with two separate sets of lug nuts and wheel locks for the front and back. Are there sites/venders that sell wheel spacers for older vehicles?

Thanks