Hi-
Ssvashon5 go ahead rebuild your holley 4 barrel. I don't think an easier carb to rebuild was ever made. For holleys, theres really no difference between the 2 or 4 barrels.

Pancake do your test again but bring a container with a couple gallons in it and drive it untill it runs out of gas. My trucks just about the same as yours tuned up good it only got 11 or 12 mpg, even now with electric fans it's only doing like 13.