1965 Z'd frame

[chopperkell]

I have a 1965 c10 long box that im converting to a short box. I decided to just build my own rear frame section. since im here I though I would z the frame up front so I can make it lay frame or at least close. My issue is I have 275/40r20 wheels and tire with 2 1/2 dropped spindles and lower A-arms with the bag mounts dropped. the frame sits about 3 1/2" frame the ground now. but looking at it with the wheels on when I go to Z the frame the back of the tire will hit the fire wall? I have not heard or seen anybody mention cutting the fire wall to clear tires?? Is there something im missing or is that what I need to do.