I believe that was to unshroud the bigger Magnum valves.
For a torque motor, the smaller valved 273 heads would be a better combo since the port velocity would be up. While I'll agree the Magnum Heads flow better, but for mileage you don't want to be spinning the motor in the higher RPM's.
Keep internals light, RPM's Down, and about 8 / 8.5 to 1 so you can get away with running the cheap gas (Your looking for economy). Shorty headers would be ok but not nessessary.
I figured the high swirl ports of the mag would be just as efficent as the small factory 273 ports with puny swirl and flow. Let me know if you guy think I am wrong. I think the 302 heads might be the best way to go but I don't have any sittin around.
As for the compression ratio, since higher mechanical compression generaly makes around %4 more efficency it would make up for the %3 differance in price and make a little more power to boot, that is why I say 93 octane. Spend a little more on a tank but drive a little farther on it. That would mean less stops for fuel and stop and go also hurts miledge.
I am not causing global warming, I am just trying to hold off a impending Ice Age!
