If an old Chevy wheel is not available, virtually all Japanese pickups had the same lug pattern as the old Chevy trucks. Nissan, Toyota, Isuzu, Mitsubishi, Land Cruiser, etc. and all their American-badged clones like Dodge Ram 50, Ford Courier, Chevy LUV, etc. have the 6-lug wheels. Most of them are 15", but just to roll it up on a trailer you don't need an exact match.
Jerry