The pilot performed a pre-flight inspection, drained the fuel tank sumps and taxied to the ramp for fuel. The refueler pulled up in a 10,000-gallon truck marked Jet-A and put 50 gallons in each side while the pilot watched. The pilot said that he was not worried because he knew that a jet-fuel truck had been converted to avgas for an airshow that had just taken place, the nozzle fit into the wing and he had restrictors to prevent a jet-fuel nozzle from being placed in the tank, and he thought that the refueler had refueled the airplane before. The pilot stated that he assumed that this was the truck that had been converted to dispense avgas. The pilot taxied for takeoff and did not make a runup because he had already warmed up the engines and completed a runup prior to refueling. He lost power in both engines after getting airborne and landed on the remaining runway. The refueler thought that the Beech Baron was turbine powered. The FAA reported that the fuel nozzle was an improper nozzle installed for overwing refueling and that the 5,000-gallon jet-fuel truck that had been converted to avgas was properly marked and contained avgas. This narrative was modified on August 18, 2005.