18 x 8 ft and 18 x 9 rear will fit; you've just got to get the right backspace and downsize the tires and roll the fender lips.
Going by my experience with 17 x 8's, 5.00 backspace, and 235/45-17's on a '65, first I'd advise you to go with that same 5.00 backspace. That might be too much, but it's a lot easier to use a 7/32" spacer (like I have on the fronts) to take out too much BS, than it is to add BS if you start with too little.
Second, I'd advise a maximum 235 cross section in front, with a 40 aspect ratio, and a 245/40 in the rear. You might be able to fit a 255/35 in the rear, but I would measure carefully before mounting them.
What rims are you looking at. (Please don't say Torque Thrust II's. Anything but TT II's, the OE rim of the Aughties.)