I'm with what blown 331 said, go with 16's no grinding and that's a common size tire these days. 8 lug 15's might get $$, that's not a common size/lug count setup IMO.

Also with 16"s your option's should be off the scale as far as rim choices. See attached pic.

You can always get Goodyear Wrangler MT II's old military HUMVEE takeoffs in a bias ply 36X12.50X16.5 can re-groove to fit your needs or a radial in a 37X12.50X16.5.

All day long for cheap, I run them on ol Red, cause I have a ton of 16.5 rims Aluminum mags/spokes/hurricanes and old style white spokes. Dodge 3/4 16"s will fit too.

You can always get some bead-locks for your 16.5's and never worry about it again.

MRW Bead-lock Wheels