bed clearance problems... help please !!!

[laidoutc-10]

I have a 69' c-10 swb, and i am assemebling a new bed for the first time and i am having problems with my tires clearing the inner bed panels. The low down..... the truck is bagged with a Air Ride Technology kit w/ K.P. componet 10" step notch kit, running a 15x8" ralley wheel with a 4.5" offset w/ 275/60/15 bfg's out back... problem is that when i air the truck down my tires seem to rub on outer skin of the bed which will not allow me to lay the truck down. It is rubbing on both sides. Truck has the original 12 bolt rear end out of 72 c-10, with cpp disc brake set up. I dont see that making a difference, any idea of what i could be doing wrong here? I have the bed put together with front bed panel front cross sill and rear brace with no other cross sills. would that make a diffrence with bed side collapsing inward ?