Fuel Economy and diff ratio

[Vombil]

I had Holden utes back in the 80s if you want an easy way of working out the diff ratio read the rev counter at 120 kph and that will be the diff ratio I have tried it and it works I also remember playing with diff ratios didn't make much difference to fuel usage should get 500-600ks per tank or top speed .253 m20 2.78 was good to drive m21 to tall in first

interesting beachy. can you go into more details re knowing the diff in the car when doing 120kmph? Sweet van too! Great pick up