Does a drum to disc conversion increase or decrease wheel offset?

[1FstChevy]

I'm in somewhat of the same pickle, since I want to do a front and rear C5 brake conversion but I'm doubting those brakes will fit inside my current 15" Torq Thrust D's... Now I plan on getting the 18" Torq Thrust Classic II which is the exact same model & size wheel that StreetKing has (https://www.pro-touring.com/forum/sh...?t=7958&page=4) +/- .25" in backspacing.

So.... Since I can't afford to do both the wheels and brakes at the same time, I guess I'm asking if it would be a decent plan to just figure out what width the C5 brakes & rotors would be, and then buy my American Racing wheels off of those measurements and then simply modify or spacer the rear drums and correct the front if necesary until the new disc brakes are in place???