Rims and tires

Those load range ratings are all well and good, but look at the NUMBERS on the sidewall. In very fine print, there is always the weight rating, in pounds and kilograms, of the tire. That is where the actual information is, not in the comparative range rating.

If you don't want Grrretchen to have too modern a looking wheel, check out
Wheel Vintiques and American racing. Both make wheels available with the 5 by 5 bolt pattern in some lovely sizes. Torque Thrust II is certainly available with that bolt pattern, and I believe is available in 18 inch diameters. You just may have to wait a few days while they custom drill the bolt holes.