What size replacement radial tire do you use for 8" rims in place of the F70x15? I am a bit confused since I have been told to use 205x70x15, 205x75x15? Ideally would like a redline radial replacement? Can you help here?

There is no exact metric cross reference to an F70-15. On my '69 I have P215/70R-15 radial tires. Some cars can take a P225/70R-15 tire, but some can't...it seems to be a car by car thing. The 215's pretty well fill my wheel wells up on the stock 15"x8" rims.

I have narrow whitewalls on my car as the original window sticker and sales contract show it being equipped from the factory with whitewalls. You can find redline radial tires from Coker Tire. I have them on a different car and they're fine tires...a bit pricey compared to commonly sold mass market tires, but still nice nonetheless.