Optimum fuel economy balance between Fast Idle and Choke

[Cardinal Grammeter]

On a 74 Datsun 620 pickup w/L18 & Hitachi DCH340 carb:


What is the optimum fuel economy balance between Fast Idle and Choke?


Engine has a thermostatically controlled air cleaner diverter valve to take air off the exhaust manifold on start and then transition to air cleaner snout.


And then there is tuning the choke spring which is difficult due to parts availability.



NOTE: I tend to run too little of each so I have to heel and toe blip for first 2-5 minutes after startup.