Regarding fuel consumption, I'll tell you mine. But you can't have too much gas. In my FJ60 starting full in Shaver lake, I added 15 gallons on the trail. and finished the trail with 1/2 tank. So close to 1 mile per gallon. On Thompson Hill and the long stretch from Thompson Lake to Ershim, you really go through fuel. It's 10,000 feet and the 2F just doesn't run that efficiently. Fuel injected, you will likely do better, but I'd recommend you start with at least 30 gallons of gasoline.
The last reasonably priced fuel going up there is at Prather. They add about $1 per gallon in Shaver Lake (as they should, it's along climb).
Bring all of your spares and tools. In 8 years doing the trail, we've had engine fires, broken sector shafts, broken frames, broken axles, broken wheel studs, broken springs, and lots of little electrical problems. I think we've been welding every year, though this year was minor. So bring lots of spares, especially if you have any unique stuff. I had a spring bushing disintegrate at the top of Thompson this year so the spring would bang around at every rock. Fortunately there were spares. This trail will certainly expose any weakness.