Paul,
The T-42/42A COCHISE is the same as the Beech model 95-B55 BARON twin engine aircraft. They were built under the same Approved Type Certificate. The U.S. Army bought 65 in total, T-42s and T-42A COCHISEs. The first T-42s were olive drab and white, later T-42As were overall olive drab. Delivery started 2 September, 1965. The U.S. Army also had five T-42As delivered to Turkey under Military Assistance Program. Seven T-42As went to Spain for the Spanish Air Force in 1972. One reference states they were built for the USAF in 1965, but that is incorrect.
The USAF did purchase some Beech Bonanzas (straight tail) to use in SE Asia as U-22s, but these had 375 horsepower engines and no ATC. Many other examples exist.
The FAA lists each 95-B55 BARON aircraft under both nomenclatures with (T-42A) in parentheses because of the common ATC. Note: there are a lot of other Beech BARON versions, about ten in all.
I have this info under a note on one of my 95-B55 Baron (T-42A)s photographed at SZP to explain the dual nomenclature.
Other examples exist-a U.S. Navy C-12 version is the same as a Beech King Air model except for the paint job. Beech also built a T-44A that had no King Air equivalent, so it gets complicated. Lockheed did the reverse-building a civilian C-130 to an ATC, selling quite a few.