Wow, those brand new Magnum 500's look killer on that car.
I also debated on the 215/70/15 vs 245/60/15 thing and ended up with 215/70's in the front. With the 245's I had too big of a gap between the top of the tire and the fender lip on my '68 Satellite. They work on your '70 though! Maybe your fender lip is slightly lower than mine because I don't see a huge rear end rake on your car. It looks perfect to me! Plus, you're running 7-inch front wheels which is the max you should run with 215/70's and I think the 245's fit the 7-inch better. I'm running a 6-inch wheel with my 215's.
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Did you get a chance to drive your car with the 215's in front and then drive it with the 245's in front? If so, can you describe the difference in front end responsiveness, control in curves and turns, and steering effort? Please tell us if you have power steering too. I keep wondering if I went up from 215's to 245's if I would see much improvement in handling and/or braking.