1969 Camaro wheel question

[confern]

Hey guys I'm having troubles finding out what the problem with my rear wheel/tire and suspension setup is. I know this topic has been beaten to death but still running into issues. Looking to see about getting any input or if anyone has had similar issues with their setups. Car is a 69 Camaro. I have 18x9.5 American Racing TT2's with 5.5 backspace on the rear mounted on BFG Sport Comp 2-275/40/18 tires. Hotchkis 3 inch lowering leaf springs (part number 2413C), Hotchkis Fox shocks with 18.5 to 11.25 inches of travel (part number 71020012) with a factory 69 Camaro GM 12 bolt rear end (part number 3894860NF). Wilwood rear disc brake kit (part number 140-7149). My issue that when I put weight on the ground to torque the leaf springs down I'm running into the right side of the tire sitting/rubbing on my rear quarter panel lip towards the outside of the car. No clearance and the tire just kinda sits on the quarter lip. Nothing rubs/touches on the driver side but not much room for clearance there either. Original quarters on the car that have never been replaced. I understand these rear ends don't sit perfectly centered and even if mine did I think I'd still be running into clearance issues. I know that the 275/40/18 has been the tried and true fitment on these cars with stock tubs and no modifications, and I want to avoid rolling/massaging the quarter lips. Could it be possibly the disc brake rotors? Any ideas??