65 at 2700 RPM is great??? This guy is going to have to sell his soul to be able to buy gasoline for that hotrod.
My 03 Mach runs at 2000 RPM at 80 MPH with the 5 speed overdrive, and I get right at 26 MPG on the freeway. My 65 with a 2.73 rear is getting right at 20 MPG at maintaining a 75 MPH speed on the freeway. Granted, it is a well tuned 289. With 3.55's, and running 2700 at 65, I would expect him to see maybe 13-16 MPG. Not good when you are paying over 4 bux a gallon. But, we didn't buy Mustangs for gas mileage anyway, did we?