I took about 1/4'-3/8" off the wheel lip. I actually wish the wheel had a touch more offset but buying off the shelf wheels was more important to me than spending $1K per wheel by going custom.
@72bluNblu has 295s on the rear of his Duster/Demon and 275s on the front. He is using a B-Body rear end, so his offsets will differ from mine. Point being, there's lots of room in the Duster wheel well for wide tire on a larger diameter wheel. I think a 10" rim is about the limit with the offset spring hangers. You may be able to squeeze a 10.5" rim if you can get the correct offset, it's not really a common width, but I did come across it when searching for wheels.