They'll fit, but....
I've got 18x8 +42 all round ('94 R33 GTST). There's about 5-10mm clearance inside to the upright on full lock (need to get out and measure this properly), and rears have about 25 mm clearance inside.
Mine looks anorexic though, which is why i've been trawling threads like these for the last 2 months trying to work out best fitment for a new set.
The lads are right, if you're going to get new wheels; might as well get a lower offset.
If it helps, here's what i've measured on my car:
Fronts
Hub to flush with guard ~84 mm
Rim edge to flush with guard ~24 mm
Inner clearance ~8mm
Rears
Hub to flush with guard ~94 mm
Rim edge to flush with guard ~34 mm
Inner clearance ~25mm
You should be able to use these numbers to see how different width and offsets will sit in relation to the guards and suspension using one of the offset calculators on the web. I'm pretty sure these numbers are accurate, but I hold no responsibility if they're wrong!
Finally, in my opinion for what it's worth, don't shell out for those Rays unless you've really got your heart set on them. The fitment won't be that great.