Trying to decide on wheel size

[Dantigan]

I am ordering my new rear axle for a '69 firebird and need to decide the width. I am currently running a 255/40-18x9 with 5.25 backspace. The car is getting tubbed when axle is put in and I would like to put some more meat in the rear. I thought about just running the stock width and getting a 18x12 with around a 8in backspace running a 335/30. Does this cause any problems or should I get the rear shortened and run a smaller backspace?



The second issue I run into is the size difference from the front. It is my understanding that the width difference should not get too extreme. I have 225/45 18x8 with 4.5 backspace. What issues do I run into having that much of a size difference? I am using BMR a-arms with ats tall uprights in the front on a stock frame. I can notch the frame for extra clearance if need be as I am going to be cutting on it for a chicane anyway. Will the frame be my limiting factor if I go with a wider tire or will it be the sway bar/tierod? If I am running a 335 in the rear what should I be running in the front?