[factorystock]

From my experience, the 250 is a solid reliable engine. The biggest issue is usually a poorly performing carburetor, as Steeveedee mentioned ( dirt and gunk blocking orifice's and or accelerator pump in carb worn). Usually, a professional rebuilt carb does the trick, assuming your getting a fresh constant fuel supply from the tank. The other issue is the extra long intake-exhaust manifold which tends to warp over time, causing a vacuum leak where it attaches to cylinder head. Sometimes you get lucky and there just loose bolts and or intake-exhaust manifold gasket needs to be replaced. IMO, this issue is the main reason GM went to a head with integral intake-exhaust around 1975. The fully synchro 3 speed in '69 is a big improvement from the non synchro unit found in '67-68 6 cylinder pickups, it is actually fun to drive, gears are nicely placed. 3.73 ratio in rear are comfortable up to 60 mph, over that, your mpg start to drop significantly.