These are the ones I'm looking at. 5 x 4.5" (114.3mm) bolt circle. The 16's have less offset and are far pricier.

Cragar 342-5712P Cragar 342 Series Black ''D'' Window Steel Wheel

If 15's can accomodate the stock brakes, I just need to know if the tires won't rub the fenders. And if the tires do clear, what's the widest I can mount?