OD on tire size needs to be 26" max i believe. My little brother is running 245/45r17's on his 4/5 '01 with no rub except when the rear end is twawked out pullin' out of our driveway. He was rubbing hardcore with 225/75r15's. The 235/55R18's you want to run measure 28.2". Too big for the 4/5.
Use this to figure out the tire dimentions in inches.....
If you do the 2/3, the front consists of just coil springs...the added 2" in the 4/5 comes from the control arms. So you can add them later to your 2/3 if you wish.
Rear wise, the 2/3 is a flip kit w/ 2" lift shackles. The 4/5 consists of that same exact flip kit, but uses the stock shackle.