Well, I took a look at my spare and it's shot anyway. Radial cracks on the sidewall.
so I have found that for the BFG All Terrain TA KO tires that I am considering The
285/70-17 E is within .1" (32.8") of the 285/65-18 (32.7") in diameter so I can use my stock rim for the spare and still have a solid road-tow worthy spare.
If anyone has tow experience with these tires I would like to hear. Reviews are good but no real info on towing a 5th wheel that I could find, but they cost enough to be good.