72 stepside 20" backspace

[MikeT72]

Hey guys, new to this site, building my first c10. I have a 72 stepside, doing a frame off, and wanting to order my wheels and tires. It is bagged, no notch, stock spindles, not wanting to do bed mods, and want to keep inner fenders. Want to run a 20" wheel, thinking the boss 338. Looking for tire size and backspace/offset help prior to ordering. Found 20x 8.5, 4.75 b.s. With a +2 offset, and 245/45/20 tires. Will these fit and tuck in? Thanks!