I was just about to say "Do not get a Kenworth T660/T800/W900." I weigh 190 or so, and I still bump both centre armrests when I go to the bunk on the 660. Then again, I've had a couple rather large trainees that squoze between them to get to the sleeper.
As for the steering wheel, if you get a truck where the wheel tilts a lot, just tilt it forward to keep it away from your gut. I don't know how much that'll help, but it's worth a shot, methinks.