To my knowledge, the only 5x4.5" BC wheels made in 15x8 are the mid-'70s Ramcharger wheels, and the six-slot "not quite cop car" Super Coupe/Magnum GT wheels (they don't have the protrusions to retain dog dishes). In either case, open your wallet very wide and bring your own Vaseline.
On the other hand, Wheel Vintiques makes "repro" 15x8s. Last I checked they were right around the $100 ea. neighborhood, about 65% of what OE Ramcharger wheels seem to bring, and they're brand new. No bends, cracks, damage or fatigue. Summit carries 'em, I'm sure plenty of others do as well.
I was really hoping you were looking for Rallyes. I have a set of 15" repros, two 7" and two 8" I'd like to sell.