I'm getting ready to do the same thing with my 62 with a TCI front clip. I've been told that the 215/45/17 up front are the safest bet. But I've seen members with 225/45/17 up front and even one member with 235/45/17 up front with some mods to the front fender lip where it was rubbing. For me I'm going to chance the 225/45/17 with a 17x7, 4in BS up front, but I do have a TCI clip thats a little narrower up front. Now for the rear, I'm going with a 17x7, 3.75BS with 235/50/17 out back, but I do have a 9in that is a 1 inch narrower than stock, also I know that a 235/60/15 works because that what I'm running presently. Now with a 18in rim I believe that a 225 or 235/45/18 would be a safe bet. I know that there are some member that have used the wheelrite tool to get there optimal tire size with out all of us guessing. So that might be best bet for your particular combo.