I had the SP2P manifold on a 318 in my 69 Charger way back. I believe the car had 3.23 gearing. Played with several carb combinations (Holley 600 and Carter TQ). I found the TQ was the best overall. I drove from San Antonio TX to Oakland, CA and averaged 21MPG during that trip. The speed limit back then was 55. That was with my wife, baby, and suitcases in the car as well. That manifold has very small runners so makes good low end grunt, not good for performance.
