For what it's worth, I checked out Diamond Back Tires. I sent them an email inquiry about 1956 Imperial tires. They responded within 24 hours, and cross-referenced bias-ply with radials informatively. I got a genuine sense of "customer care". I believe one can download their online catalog, in Adobe Acrobat format. Does Coker Tire "feel the heat"? :-) Vince in Boston