Limited tire sizes for stock 18" rims.

I'm new on this site and have a 2007 2WD Titan. I have a PRG leveling kit w/ 1" rear lift en route. I really don't mind the stock rims, but have discovered it's a pisser trying to find many tire size options for 18" rims (like alot of guys here). I'm trying really hard not to give up the quiet/smooth ride I have with the stock GDYR SR-As, but also know it's virtually impossible when going to an A/T. Without entering the E-rated 285/65R18 10-ply heavy-duty tire, the biggest I can go is 275/65R18, which has a shorter aspect ratio and appear small on the rear. Cannot find 275/70R18 in any A/T tire. Yes, I want my cake and eat it, too. Wish Nissan had stayed with the 17" rims; more sizes to choose from. Any suggestions???