79 4spd burb milage

[jims72]

Well now that I have got ol yeller running I have decided to try and get the best mpg out of her I can. im shooting for 15mpg. yeller has a 350 4spd and 1 ton running gear. I believe her to have either 3.73 or 4.11 gears but im not positive. She does about 50mph at 2k rpm in 4th with the sm 465 in her. She is all stock except for a 625 carter afb. I intend to switch to a Q-jet soon. The burb is stock height and runs on 245 75 16's. what can I do to get close to my 15 mpg goal? My neighbor mentioned switching over to a new venture 5 speed from an 80"s model 4x4 which sound ok to me. what can I do here? Im currently getting like 7 mpg and its just not acceptable. it is a 4x4 too.