I put a set of 275/35-18 Nitto NT-01's on a 9.5/10.5 wheel setup this evening. They are bulgy on the 9.5 and pretty square on the 10.5. They fit like 285's and would be perfect on 10's.
A 275 might sound small for a 10" wide wheel if it was a street tire, but the NT-01 runs really wide. You will have tons of room to the inside with this 275 on the 10 ET25 wheel, and it will completely fill it out.