68 GT convertible project

Wheel and tire specs will definately be critical. For the rear, I'm thinking about using a 255/35R20 or a 285/30R20. They are roughly 27" in diameter. For the front, I'm thinking about a 225/40R18 which is 25" in diameter. Those sizes would give me a 3" sidewall on both the front and rear.

I really need one of those adjustable wheel fitment tools where you can mount a tire and figure out all your wheel measurements. I doubt anyone around here has one to borrow though. Before I worry too much about it, I need to buy front brakes and get them mounted. Need to save up for a little while.