Cruise Performance

[Tom]

I have a normally aspirated 1965 337. I use 25/25 for climb, then let it accellerate at climb power at level off (3000-5000 ft) then slowly reduce power to 23/23. My GPS and LORAN usually indicate a GS of 130 kts.
(I know GS is dependent on winds) I true out at between 140-145 miles (ASI is in miles). Is this normal? The book says I should be getting somewhat better. The engine compressions are all over 70/80, fuel flow is about 10gph/eng. The plane seems to be in rig. The paint is not great but I've seen worse. I fly mostly XC between Chicago and northern FL. All things roughly being the same, the numbers are consistent. What do you fellows think?