DOD strategy called for ultimate transfer of all A-7D’s to the Air National Guard.  Unlike the USAF, the Air National Guard determined  that a two-place combat trainer was needed to assure the maximum in combat training effectiveness .  Negotiations began for a two-place version of the aircraft.  Designated the A-7K, it retained all of the features of the A-7D and was fully combat capable.

A-7:

Genesis of the Navy Attack Bomber, Light (VA(L))
In Comat
Farewell Proud Bird
Aircraft Performance Perspective
Low Altitude Night Attack (LANA)