Freeway driving and carb secondaries

[Mrturner1]

Hey there, I had a question about my carb and the secondaries during freeway driving. The truck is a 1970 c10 with a th400 and 3000 rpm stall. The rearend is a GM 12 bolt with 3.73 gears. When i'm on the freeway doing 65 mph my tachometer says 3200 RPMs and, now I know that's a little bit wound up but what I'm wondering is MI into the secondaries on my carburetor or not? Because I would make a huge difference in miles per gallon on the freeway.