Twin Turbo 1971 Scamp Project

Bill- my drivability is in reference to the achievable power + mpg. Thats what streetable is to me. My magnum powered car feels quick, has a steady idle, plenty of vacuum, but it strains to do better than 12mpg and thats if i have the car at an unpleasant 50-55mph on the highway. Neither of which are good when i have to drive 50 miles(one way) to go racing.