Find it hard to understand the mileage issue with out knowing more of the basic information such as..... tire height or tire size, rear end gear ratio, MT or loaded, flat or hilly and at what speed.......
My stock rebuilt 261 will give me 12 mpg driving at 32 mph with 2000 rpm in high gear with 6.5 rear end ratio....tires are 10:50 x 16 at 36 inches high....... running a Carter YF and a paper filter instead of oil bath ......... happy with anything over 10 mpg. Oddly enough, the mileage barely changes whether I am doing 2 wheel drive or 4x4 on dirt roads at same speed.... suckes gas real good in low range 2:1 in 2nd and third........ oh top speed is 44 mph in hi gear on flat pavement.... 2900 rpm..... front end is square like a brick.....
