offset shackles (how big a tire)

i put them on this 67 i have. i had a hell of a battle to put 28x11.50 hoosier dot slicks. they wouldnt fit on 10" rims. had to go to 8s. i had to remove the outer wheelhouse and weld 1/4" rod the lip of the wheel well after i removed the opening lip. i know of a guy that fit the same tires on his scamp without removing the outter wheelhouse i think maybe he pushed it out with a jack. if he did you couldnt tell from outside. i built the rear for the car so im using 3.5" bs draglights. figured make the dana as short as possible to save a few ounces.... i also know of guys that squeezed 275s on darts without the offset hangers. im thinking of making my own setup for my 69. i really hate the relocation box deal if i felt the need for that much tire i would just go ladder bars inside the rear rails.