You will find a larger variety of tires in the 70 size than 75.

Tire developement has been going along with tire size.
IOW, when 70 series became the rage the tire companies spent millions on development; rain, grip, noise, etc. Then it was 60 series and the 70 series were not concentrated on much, but received some trickle down from the 60s. Now it is on to the ridiculous series, i.e. 45 and 55...

So, 75s are really old and 70s are sorta old.
Go with the 70s.
Buy Michelin or Dunlop. I happen to think that Dunlop D2 are very good on these cars.

__________________
Ed
1981 300CD (Benzina)
1968 250 S (Gina) 266,000 miles!
1983 Alfa Romeo GTV6 (Guido)
1976 Jaguar XJS-saved a V-12 from the chevy curse, what a great engine!
1988 Cadillac Eldorado (better car than you might think!)
1988 Yamaha Venture (better than a Wing!)
1977 Suzuki GS750B
1976 Yamaha XS 650 (sold)
1991 Suzuki GSX1100G (Shafty Gixser)
1981 Yamaha VX920RH (Euro "Virago")
Solex Moped
1975 Dodge P/U camper


"Time spent in the company of a cat, a beer, and this forum, is not time wasted!"