the combo you suggested makes your back tire about 2'' taller(28.8'') than the front(27''). I doubt that is the look you are going for. If you chose a 305 35 18 in back and a 245 45 18 in front, both tire would be the exact same diameter of 26.6''. if you keep your offset at +40mm or less (7'' backspacing) on the back tire you should be fine with no contact issues. The front are perfect.
__________________ 97 Cobra-03 Cobra t56 and alum DS, SPEC111 clutch, FRPP 4:10,T&J Performance Forged 4v(8.9:1), Manley rods, Novi 2000 w/ Fast Track A/A I/C, Barry Grant Fuel syst., BBK longtubes and H-pipe, MSD ignition, Detroit True Track, Magnaflows, 315 NT01's on 17 x 11's, KB BAS, SCT tune and about a million other things. 575 RWHP. Going into the shop this winter, looking for 650 RWHP. | 
Help on Tire Sizes 
