Would pretty much agree with Jerry (Hotrod Lincoln) except would start with 1 turn instead of 1 1/2 on pre-smog (1968) carburetors.

And 310kms per 60 liters is about 14 1/2 miles per gallon - not too bad.

Check your tires for proper inflation, and also check to make sure you do not have a brake that is dragging.

Jon.

Good carburetion is fuelish hot air
The most expensive carburetor is the wrong one you attempt to modify.
If you truly believe "one size fits all," try walking a mile in your spouse's shoes!
The Carburetor Shop