15x10" wheels on '82 Series 75

[Dave Burden]

I have a line on some 10" wide wheels for my '82 Series 75. Nothing fancy, just steel circle track ones. I will be using them for autocrossing and hillclimbs (solo I events). I don't have them yet and the current owner says there are two different offsets. What offset should I be looking at in a wheel this wide?

Thanks,
Dave