I know a mate of mine had a HG Monaro and he had (I think US DRAGWAY Mags)made for it and he run massive <br />rear tyres on it without popping the guards and what he did was fit the tyre in the front and rear without any rims (propped the tyre out to 8 inches for wheel width) and made a jig to messure the offset required. Now the front and rear were different because he had a nine inch in the rear ( axles drilled out for Chev pattern). As for size I know he had bigger than 245's but all you have to be is 1/2 inch out of centre and you are in the shit creek.