I have gtr et 30 all round 18x8.5 f 9.5 r with 225/40 f 255/35 r had the rear rolled flat back and light roll on the front had to have 3mm spacer on the front though as my coilovers are massive and ancient lol so to be safe I would suggest et25 for the fronts but I know alot of people run et30 no issues depends on your suspension set up
I'm not running hardly any camber though and have a skyline diff and shafts which I am sure pushed the rears out a little further as dean had the same set up on his and his sat better than mine. But as I said I have loads of room inside edge so if they were et35 would be sat in a little further.
Have you had a look through the wheel thread?