390 fuel mileage and HP

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

Ranchero , I have a 69 mach 1 with a factory 390 in it and when I checked my fuel mileage I got 18 to 20 mpg (that's when the pedal isn't to the floor) and I'm sure it has 3:55 gears in it to. As far as hp , I'd say at least 350 hp although alot of guys say that's wrong but you couldn't prove that to me. Don't worry it'll fly down the highway if you want it to.

Rocky

390's are great engines, run forever, but gas mileage was never their strong suit. Your headers will help, and the 650 Holley can be tuned for economy easier than most. The gears would be a drawback, too much RPM at speed, an OD trans would help. I've seen 390's get 20 mpg (that's about 14 US) driven in the real world, with maybe 20% more if you baby them. A 69 Mach I is slippery, might get better than that.The '68 Ranchero is still the smaller body, isn't it? That'll help, too. When we ran big block 'Tangs, mileage was the least of our concerns.

Thanks rocky and pope the 67 ranchero is a small truck that weighs around 2900 pounds thanks for the advice