Welcome to CHR David. Like Power said, what is your definition of good gas mileage??? Running 11's and good gas mileage with a chebbie pickup shouldn't even be in the same sentence!!!! A stock v-6 or a low budget small block sure isn't gonna do the job. You wanna run 11's while running an overweight tank down the track it's gonna take a lot of motor, lots of chassis work, and lots of $$$$$$$$