Magnum 500s on a Duster/Demon?

I got four 15x7" wheels, no tires yet but planning on Firestone Indy Firehawks, pretty much the only choice out there for street tires on 14" or 15" muscle-car wheels besides BFG Radial T/As and I don't like them very much. Looking at tirerack.com it seems like the really wide street tires like those only come in 15" wheel size.