Some of you need to go back and read the entire thread, many of the questions being asked have been asked and answered a couple times.

4speeds has it right on, except I have a brand new LD4b intake. I also have a 190 tstat and electric fan a LU 904 tranny with low 1st and 2nd gears. 2.76 gears. Manual steering no ac no power brakes. Light weight aftermarket scat I beam rods. Electronic ign. I get about 5 mpg better now than the when I bought it with the bone stock #s match 318 2bbl. I have to use premium gas but it is still cheaper to operate than before with a nice bonus of more HP and TQ derived from burning more of the fuel when it counts, in the engine not the exhaust.

I think the mag heads would be about the same mpg with a little more WOT HP.