JUst a lil FYI trash here..
Cruise speed: 205 knots
Range: 910 nm (1,048 mi, 1,686 km) at 216 mph (347 km/h) at 8,000 ft (2,440 m)
Service ceiling: 26,200 ft (7,988 m)
Rate of climb: 1,700 ft/min (8.63 m/s)
In 1984, the Beechcraft 1900, a pressurized 19-passenger airplane, was the follow on aircraft.
If you will look the best range/speed for this aircraft was at 8000 feet at 216 mph so its typical flight profile was around 9000 to 11000 feet. LOL..I mean the plane was an ad hoc abortion of spare parts...Queen Aire Wings and King Aire Engines and nacelles...anyways...I couldnt find a Dash-10 on it but the specs are from Wikipedia...and you will notice that a preasurized version didnt show up till 1984.