Bryan, I'd check into that. It seems like I've heard of people running smaller rims on one with a disc conversion. Mine was drums and I had some old 16.5x10 rims on it. Just keep the pressure over 10-12 psi and you should be fine as far as unseating the bead goes.
Since you have to buy rims anyway, call Stockton Wheel and see if they have some custom jobs in a smaller diameter that will clear. They have custom rings and centers on hand, so they can make a rim any way you want. They do alot of hotrod wheels. They can take a set of 14" diameter rims and cut the outer ring off and using their custom rings, they can turn them into 17" wheels, or whatever you want. I've heard it's not too expensive either. A buddy of mine had custom 16.5x10" rims made to fit his five lug CJ, so he could run surplus Hummer tires.