Pretty much any GM 6 lug wheel '70 and earlier on 2wd and '87 ('91 for 'burb and Blazer) for 4x4 rims will work. Avoid the '88 and later 6 lug rims, the offset is different and will rub. You could also use some jap truck rims, but again, there's some offset issues, especially on the solid axle trucks.
