Performance mixed with fuel economy!?

The compression is really a big deal. Normally, Chrysler engines of this era blueprint down into the 7s. They are never actually as high as they are rated. Never. If you can get compression to somewhere between 8.8 - 9:1, that's really the sweet spot for MPG and performance mixed. Ant more and the risk for detonation during heat soak is there. Any less and mileage and performance take a hit.