In the normal evolution of the aircraft and propulsion system, the second lot of A-7 aircraft was  upgraded with the TF-30P8 engine, rated at 12,200 pounds thrust, and was designated the “B” model.  A total of 196 A-7B's was manufactured in a single lot under contract number N00019-67-C-0082.  The A-7B model had exactly the same structural configuration as the A-7A and could be distinguished externally only by the serial numbers.  The A-7B was 1308 pounds heavier.  The TACAN and radar altimeter systems were updated to later models.  Performance was improved by approximately eight percent with the upgraded engine.  The A-7B first flew on 6 February 1968 and the first squadron deployed aboard the carrier U.S.S Enterprise on 6 January 1969 and entered combat in Vietnam with squadrons VA-126 and VA-215 on 4 March 1969.  As did its older brother, the A-model, the B-bird had a productive combat tour with small losses and high target destruction rates.

A-7:

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