I have a 76 F-250 w/ 360 2bbl with headers and the four speed w/granny low also 4:10 gearing. the problem is that i am only getting 6 miles to the gallon city and 8 highway. i talked to my father and he sayed he used to get 12 mpg with his (same set up) i think the carb is over jeted and am planning on putting a edelbrock aluminum intake and a holley 600 cfm 4bbl hopefully gets better mpg.