I started with the wheels first. I have 18 x 11 with 5.5 back spacing. I am cutting the quarter lips down from 1 " wide to 1/2" wide and will also be rolling the lips. That will give me approximately 5/8" clearance from the quarter to the tire sidewall. With everything mocked up this way my rearend measurement from rotor hat to rotor hat (not axle flange to axle flange) needs to be 56". Right now if i drop a plum bob from center of inside quarter to center of inside quarter and measure the width from inside string to inside string with uncut quarter lips my car measures 69 3/4". If you are running just about any rear suspension other than leaf springs you should be able to put a 12" rim with a 335 tire but you have to get the back spacing dead on. PM me you location/phone number if you have questions. If you are close to Sacramento, CA. we can use your rear end and my rims and tires to check out your car and mine before I cut my rear end and you order wheels.
18x12/335 5.9"bs my rear end is 57" wheel mount to wheel mount. I purchased my wheels first and had the axle built to the wheels.
__________________ Steve Hayes
"Dust Off"
68 Camaro
Speed has never killed anyone. Suddenly becoming stationary, that's what gets you! "Jeremy Clarkson"