Can I fit a 18x8 with a 48 offset on an r56 without issues ? Car has nm springs ( I think that's like a 1.25 inch drop) ????

 

The wheel is OK but with the suspension drop of that amount you have to find a tire that will not rub.

You can go with a narrow tire and stretch fit it, plus dial in more negative camber to tuck the tire inside the wheel arch. You can dremmel trim the plastic wheel arches wherever they are rubbing.

Or you can go with a tire that has slightly less tall tire diameter like-
215/35-18, like the Sumitomo HTR Z III for #115 each, 300 treadwear, 24" tire diameter.

This might be very close-
Michelin Pilot Super Sport
205/40-18, $181 each, 300 treadwear, 24.5" tire diameter is nearly OEM.
This is a very good street tire, comfortable and handles well. If you roads are bumpy and full of potholes, a 35 series sidewall is going to be very rough riding.

 

I think you might hit the spring/perch with the wheel/tire. But I don't know for sure.