I have a 68 390 that i have in my 67 ranchero, the engine was just rebuilt with stock internels but i put on a set of hooker headers, edelbrock performer intake and cam and a holley 650 street avenger carb. This is all backed by a c6 with a shift kit, a boss 351 rear with 3:55 gears and 18 inch wheels. Can anyone give me a guess on the horsepower of the engine and how bad will my fuel mileage be and how do i tune it for more fuel efficency, also the engines throttle response is slow is this a rich carb setting or what? Thanks for all the help