The Owner's Manual for '71 Sqbk says tires should be 6.00 15 in. (I do radial, of course.) But I have all 6.50 on the car. Don't know how that happened. So...how important is that size? Is 6.50 OK? Front tires don't scrape fenders on sharp turns. I'd guess that At Least two in front, like two in rear, should be the same... but don't know.