Updated for older Dodge fans:
One of my 16.5's blew out on me in the N.Arizona boonies where I would have had to wait a week for a replacement (and my spare was pretty much junk). I had no choice but to change to the 16" wheels but was lucky enough to find a salvage yard that had 2 used rims at a reasonable price. I bought two new Uniroyals that were $36 less per tire than what 16.5's would have cost and mounted them on the rear (couldn't afford to do all four). Rims from up to about '93 will fit and the overall outside tire diameter is nearly identical to the 16.5's on the front(so there is no need for two different size spares). When the fronts wear out (or blow out!), I'll switch the fronts also to 16's.....