Here's what I am running on my 68 Convertible. I could get about .5 in more backspacing in the rears, but for my car, this appears to be the max I can go, and not cut the tires. When I re-do the paint, I'll roll the fenders, this can be done without cracking the paint, but takes time and patience, Eastwood sells a nice tool for this. If the fenders are rolled properly, you can't tell without getting into the wheel well. Each one of these cars is slightly different, they weren't perfect from the factory, and after 40 years haven't gotten any straighter. Go with a new set of leaf springs, put the 5 leaf vice the original 4 leafs, will give you a bit of added height, and when they settle they will sit close to stock ride height. You could also order a set of leafs that will give you a 1 in. height increase in the rear. Feel free to PM me, I'm sure you can get this worked out.
Fronts:17x8 4.75b/s Torque Thrust II 235/45/17 BFG G-Force
Rears:17x9.5 5.5b/s Torque Thrust II 255/45/17 BFG G-Force