The next variant was the Do 217 K-3. A revised anti-shipping version, the Do 217 K-3 was similar to the K-2 but fitted with improved missile guidance equipment to allow the use of either Fritz-X glide-bombs or Hs 293 missiles. 40 were converted from M-1 airframes. It was given the K-2s larger wings. When fitted with external ETC weapons racks it was named the K-3/U1. It had improved armament, a MG 81Z and MG 81 J in the nose. The K-3 did not roll off the production lines until the beginning of 1944. The Dornier Do 217 M-11, its intended successor as the standard missile platform, was only produced in small numbers owing to slight production capacity.

Sources:
Gunston, Bill - The Encyclodepia of the Worlds Combat aircraft, 1976, Chartwell Books, Inc., New York
Brown, Eric, Captain - Wings of the Luftwaffe, 1979, Airlife Publishing Ltd., Shrewsbury
Gunston, Bill & Wood, Tony - Hitler's Luftwaffe, 1977, Salamander Books Ltd., London
Donald, David - The Complete Encyclopedia Of World Aircraft, 1997, Brown Packaging Books Ltd., London
Wikipedia - Dornier Do 217