I don't have a 350C just a plain old TH350. The tires I have are the mastercraft Courser M/T's, there probably about 50-60lbs as most of these 33's are about 55lbs or so. Also the carb wasn't tuned just right and while I'm home here my Dad helped me tune it better so now it's a much smoother idle and runs much better than before. Also with those big huge tires on it, and it's old and the steering is worn and has quite a bit of play in it, I think I was only averaging about 55 maybe 60mph on my trip up here. I'm used to driving a little car, and this truck is big and seems like it doesn't fit in the lanes. Anyway, I'll have to see what the mileage back is on the 30th. It may be a bit better we'll see.