Ok I've been reading a few post about there mileage being down on the 360/390 of around 10-12 mpg. Well I have a 302 in my 79 sb with a Edel. 600, headers and dual exhaust. Nothing else, stock rear gear (3.25) stock size tires and no emissionns. I get between 11-12.5 and that's on the highway and I baby it. It's all tuned up, no sticking rear drums so what gives for a measly 302. Why such crapy mileage?