265/40 and 285/35 are both correct and will get you within stock specs for rolling diameter. But for 10.5" wheels, you'd want 285/35. 265 would be if you were running 9" wheels. 265 on a 10.5" will be stretched (I run 275 on 10.5" and there is already slight stretch).
Running a 30mm spacer is probably not recommended. +15 will poke out unless you're slammed, it will tuck if you're low enough. I'm at +0 in rear on my first gen and the rim barely pokes out, but that required camber and lots of fender work.
Don't buy spacers before test fitting your wheels. Fit your wheels, take some measurements and then buy spacers if needed. It's your car, the look is yours, not anyone elses. Everyone has a different opinion on fitment and so on. And people have very different definitions of flush. I think my car is flush, some people think the wheels are way too aggressive. What others consider flush, I consider to be very tucked.
For spacers, really anything that is hub centric will be fine. I get mine through eBay since I swap a lot of sets out. So far, I haven't had any issues with vibration. If you need 15mm or larger spacers, I'd highly recommend bolt on style. Much easier to install than the kind where you have to press in new studs, plus you don't run the risk of damaging your hub bearings when pounding out the old studs.
