Something different Building for MPG.

Hmmm....Good question. 318 with the smallest port heads and combustion chamber I could find. Heads should be iron too. Cam would be roller with no more than 200 degrees of duration @ .050. Aluminum roller rockers to reduce weight and friction. Roller cam bearings. 200 degree thermostat and port fuel injection. Electric fan. Manual transmission and a 2.73 rear gear. Aluminum driveshaft. Synthetic oil in everything.

Fiberglass hood and trunklid. Anything and everything to reduce weight and friction.