I have a '59 Super Rocket that is geared up one tooth on the front sprocket. With a K70 350 x 19 the gearing was perfect, but they wear in the middle and tram track when worn down. Next tyre is a TT100 410x 19 which has a smaller rolling diameter and has geared it down. From looking at other tyres rolling diameter I have found the K70 to be the tallest and will be fitting another when the time comes. I like the gearing and the look of the tread for that era motorcycle.
Why do people fit wider rims and tyres? AFAIK tyre sizes were widened to get the power to the ground, this isn't an issue with a 64 year old 650cc motorcycle.