Yeah, that is common story about radial tires causing the rims to flex and pop off the full wheel covers. But really all the full coverage wheel covers I have spin off in a few blocks, no speed turns involved.
165Rx15 is the VW Beetle radial equivalent tire, most common, and therefore cheapest and easiest to buy for a HJ.
175Rx15 is uncommon because it was used on later Volvos which were larger than HJs & VWs.
195Rx15 was actually the standard tire on full sized Chevy trucks of the early 1980s and Mopar miniVans!
205Rx15 is about the biggest you can use on Studebakers with out having rubbing problems.
215Rx15 is the biggest you can use on 51-55 Kaisers without rubbing problems or problems installing the wheel & tire under the rear fender (the bumper jack + axle jack requirement).