Sorry for the really late bump, but looking into almost exactly the same wheel setup as you. I'm assuming that the 10.5 along with the Nankang 275's won't clear without the 5mm spacers on the front oem perch, which is why you're using a spacer? Trying to make sure before I pull the trigger on a set of TE's in 18x10.5 +30, wrapped in 275's someone is selling.
If they're a good deal then buy them regardless. Easy enough to buy the spacers after you get them if they need them, spacers are cheap compared to the wheels. But yes you'll most likely need a spacer. My 18x10.7 +38's need a 15MM spacer so that'd be effective +23 offset. I definitely could not go any lower of a spacer. A +30 with a 5mm spacer would bring it to +25 but the wheel itself is .2 inches less wide so should be about the same fitment.
I'd recommend doing a stud conversion (75mm) but otherwise yes you need longer lug bolts. If you buy burger motorsports spacers they'll come with longer lug bolts by default.
