What Do I Need To Do?!?!

OK..I bagged my truck on 20s with 255/35/20 all the way around. My problem is..when I lay it out..the rear tires hit the inside of the bed..not the fender well..but rub inside of the bed just opposite of the outside panel..I think it's double thick..can I just cut this out?..What do I need to do? Please help..thanks.