Tom, they're Center Line Wide-5s.
Unless you have a flared body, you'll have to do some modifications to use the big fat guys. I had to bring all my wheels in three inches to make them work.
They're true riveted wheels, dating from the 60s racing scene. You'll be able to find them at Pacific Customs (for sure; not positive about other places) in whatever size you want. They bolt onto the CB Performance disc brakes I bought for all four corners.
My back tires are seven inches wide (four-inch outside offset; three-inch inside offset) and six-inch fronts with a three- and three-inch center.
I'm using 21" Kumho tires. I'll get the numbers off them for you this week.