318 heads

If you’re really going for mileage, get a 239 LA or Magnum V6 to retrofit in and gear it with 2.18-2.45 gears for a fifth Avenue. I got one in a 90 dodge truck with a five speed and 3.90 gears and it’s begging for 3.21 or 2.94 gears. I can pull out in third gear. Mileage still goes over 20 during mild cruising.