Good job! Yes you may need a re-jet. If it's jetted for 5000 ft and above it's probably got #47 jets in it. In OK you'll probably be good with #53 or so. (Someone else please chime in if this is not right for OK.) I just picked up some generic replacement seat belts at Advance for my trail rig for when I have the back seat in it. They will work good as long as you can use the stock reinforced anchor points. Best for fumes in the cab is to run the exhaust out behind the tires and to the sides. And don't run with the rear window in the up position!