When I bought my K20 in 1977, I installed 8PR 7.50-16s on it. Best I can recall, they were Armstrongs and looked like the attached pic. Made my only real cross-country trip in winter with those tires (I have never run highway treads, kinda defeats the purpose). Went from N. Calif. to eastern Kansas and back, at least 3600 miles I believe. Of course they made some noise but that's to be expected. I never got stuck with them, even after a snow plow driver piled up a bunch of the white stuff on the wide spot where I pulled over to get a little shut-eye. His plow partner said he figured they'd have to pull me out. They didn't.
Bias-ply tires with nylon cord casings would flat-spot overnight, no matter the tread pattern, but a few miles or so would smooth out the ride. Rayon cords did not seem to flat-spot, or at least not as much as nylon.