Fender Wells

I just bought a 83 GMC Dually & I'm planning on laying frame with some 22" wheels. I know I will have to narrow the rear end & raise / stretch the Dually fenders up, but will I need to widen the inner wheel wells to fit the 22s in side the Dually fenders? I want to find out before I raise the bed floor so I can bed line the inside of the bed after I've raised the bed floor.

you will need to tub the bed

How Much? I don't know any body running Semi wheels to measure theirs. Should I just bring them in even with the outside of the frame rails? Like I said, the time for me to do it Is while I'm raising the bed since I'll be cutting at the bed then & bed lining the inside after words.

I have a C&C rearend W/22s they stop right at the leafspring pad.