Tires and wheels with spacers

[Ak-Amarillo]

I have a set of 38-15.5-16.5 radial swampers on 12 wide weld wheels. I want to know if running a 2" spacer will let me run 16.5 wheels on my 06 f350? and with 2" spacers will they stick out way to far? I understand backspacing is a big deal these have a really deep dish