There are two sets of OZ Futura:
17x8.5 ET 19 18x10.0 ET 17 non-US S4
17x7.0 ET 23 17x 8.5 ET 30 US S4 (the S4 OZ wheel (Lotus Design?) being discussed are of these dimensions)
I have OZ Futura US spec S4 wheels on my 88 (Citroen transmission).
OEM lug bolts are around 25-27mm - I needed at least 33mm (and went with 40mm) - front.
I also changed the front hubs from 60mm to 58mm (rather than machine out the wheel hub hole - to keep maximum wheel structural integrity)
The rear had 50mm adapter with STUDS because of my Citroen ET -20 (negative 20).
This gave me OEM offsets (not flush with fenders).
Back to Mike: If you want these S4 wheels to be flush, I recommend you fit them NORMALLY, then measure the distance needed for a spacer.
I don't believe you need any adapter for initial use(although you may need longer lug bolts front/rear since you have Renault transmission).
You may have to bore out front wheels to 60mm or change hubs to 58mm like I did.
For the I'm guessing you'll need at least 30mm spacers, but verify it - don't rely on my SWAG.
To be hella flush like this G Esprit