Deep dish on a stock 10 bolt rear

[elctron02]

I have a stock length 10 bolt and want to put 19x11 wheels on the rear. Right now I have drums, but will convert over to disc. I want to put a deep dish wheel. Something like a 6" lip.... Will I need to cut and narrow the rear end? Will I gain more clearance / backspacing going from a drum to disc?