You also need to consider external versus internal balancing of the motor. Hense the differences in 28oz vs 50oz. the motors harmonic balancer is also different. I did this conversion with a 302 in a 73 Mustang and AOD years ago. I did end up getting 30mpg when I was done, had the 2brl, AOD and 3.00 gears and kept my foot out of it. The darn thing was just about 1100 rpm's at 60 mph. On a drive from Sacramento to Burbank I used 1/2 tank of gas.