Not sure of the off-set numbers......
These are 6x10 Mercury wheels with 1" spacered drums and discs up front.
They stick out beyond the standard arches.....just a wee bit.

Sorry to resurrect an old-ish thread, I have a set of 10x5" Mambas (offset 0) and am trying to work out if I'm better to either a) buy new wheels with a positive offset or b) buy new arches.
My question is, do you have any issues with scrubbing the tyres with the above set-up? My Mambas sit very similarly (on the rear, haven't got the fronts sorted yet).
I would prefer to keep the Mambas if I can but it's not legal for any tread to not be covered by bodywork (from above). I have someone who is willing to buy my Mambas but I will lose about the same as buying new arches either way so if I don't need to modify the inner arches at all for the Mambas then I may just find the right arches for the job.
And yes, it was stupid to get my arches sorted before having my wheels, unfortunately that was the way the timing fitted with my mate who painted and fitted them.