Cruise Seems Lean

I am running 2 660 center squirters on a tunnel ram. I am wondering at what throttle position do these carbs run on idle circuit vs transfer slots vs main jet. I have a cruise RPM of 2400 but looking at the spark plugs, it appears it is running lean. I am getting great fuel mileage, but I am concerned with the mixture. Idle screws were 1 1/4 turns out, idles and starts great. It also was 5 hours of driving in high 90 deg / Low 100 deg temps and sustained RPM. The coolant temp stayed mostly 190-200 deg for the trip, climbing to 210 at stops. I am not sure if idle mixture adjustment, more transfer slot (or less) or more jet. Unfortunately I do not remember the amount of transfer slot or what jets are in it at the moment. Engine is a mild, lower compression 440 with a Hughes Whiplash 440 cam. Converter is 2400 stall B&M, rear gear for the trip is 2.94.