The offset will have no impact on how much protection a tyre will give a rim as if the offset changes (moving the wheel in/out) the tyre will move with it, giving exactly the same amount of rubber protruding past the rim.
Also, 8" wide with an ET of 45mm will nicely fill the arches. If anyone was being picky and wanted a "flush fitment" like the cool kids have, you could add a 5mm spacer, but I reckon it'll look spot on without anyway.