help with gas mileage, this 67 needs to be on the road more

[The Big Green]

I have a 67 Chevy SWB with a 350 and the gas mileage is about 10mpg with 11 here and there on a good day...lol. I got the truck when I was 17 and I'm 27 next month. When I was 17 and gas was alot cheaper and I didn't pay for gas anyways, I put in a new rearend with 4.11 gears. I don't like the gears now, I mean they are fun in town but I run 3,000 on my 35 mile trip to the city, I live in the boonedocks...lol. I have a 350 probably bored to a 360 with 11.1 popups,300 Lunati cam,282 stock heads with the 1.94 valves. I have a Edelbrock Victor Jr. intake, pulls at 3500 to 7500 I think. I have a crappy 750 holly that I bought and it falls on its face sometimes when you hammer down and it runs really rich, burns the eyes when you stand behind the truck. I wont buy another carb from a place that rebuilds them. How can I get better gas mileage, gas prices are high and I just hate to see these old trucks sit because gas is high. I know the 4.11's are killing me and that 750 and cam and pistons love the 3grand rpm's for 35 miles. My first ideal is a 3.42 gear. What does everyone else think? I know I wont get 20+mpg but 10 just sucks. Oh, and I built this engine about 4 years ago and will be tearing it down for new rings and bearings so it would be a good time to do things different. I don't want to go stock but I will if I have to. These trucks are 5000lbs and its like pushing a piece of plywood down the road.