How can I tune my engine or carb to get better mpgs?

I have an 85 F150 300 inline 6 with the 1 bbl carb. I currently get about 10 mpgs. How can I tune it to get better? I have only 1 cat, no muffler, no o2 sensor. I dont want to mess with the exhaust too much cause of the way it sounds now. Any help?