My 16x6 alloys have very little offset, less than most other 70s. It was part of the trim as mine never had extended arches either. I also can't fit 15" rims to mine despite most other 70s being able to take them - my front calipers are too big.
Chas if you're interested these alloys are up for grabs still, I keep toying with the idea of fitting 235/85 fedima rip-off centipedes to them and using them for playdays but I really don't do that many playdays! There's a set of 5.
Jim.