mpg on my 340

Best tricks for mileage are timing setup - and run the vacuum can; and tire pressure/alignment. Pump the tires up tto the "maxpressure" noted ont eh sidewall. Make sure the car's alignment is good. And tune the timing first with the vacuum can, then tweak the carb. I've gotten 17 in a 383 C body with 3.55s, a customer's 496 is getting 13 on the highway and makes just shy of 600hp, another with a small block 422 has over 20K on it and gets over 17. It's all in the parts choices and tuning.