Gamera
Hmmm very interesting. Just starting to think I know a little about different versions of the M4 Sherman and all this about M48 and M60s just blows my mind...
The M48A5 is a very late tank, even later than the early M60A1 tanks. There was a vacuum formed when the M60A2 with it's gun/missile launcher failed and the tank was removed from Active Army service. It was never fielded to the Reserve Component.
Those tanks were replaced by the later M60A1 RISE/Passive tanks in the Active Army. Those tanks were intended to round out the USAR and ARNG tank battalions. So now there is a shortage of medium tanks.
So older M48A3 tanks were upgunned and upgraded to M60A1 fire control standards and called the M48A5. The tanks were fielded to a few National Guard divisions, 49th AD, 50th AD and 40th Infantry Division, perhaps some more. The Regular Army used them in Korea with the 2nd Infantry Division.
As the Regular Army transitioned to the M60A3TTS, it freed up M60A1 tanks and those tanks went into the USAR and ARNG to replace the plain M60s and M48A5s. The two tank battalions in Korea went straight to the M60A3TTS. The battalions liked the loader's M60D the M48A5 had and cut the mounts off the tanks and placed them on the M60A3TTS.
So during a time in the late 1980s, the Total Army Armor Force used M60, M60A1, M48A5, M60A3TTS, M1IP and M1A1 tanks, with a lone M551A1 Sheridan battalion. I worked for the Directorate of the Total Army Armor Force at Fort Knox for a few months in 1991 and remember one of my tasks was trying to determine which version of tank each battalion used. It was a very big spreadsheet.
As a post note, the failure of the M60A2 led to the cancellation of the proposed M48A4. If the M60A2 was successful, older straight M60 tanks were to be converted into M60A2 tanks by removing the original style turret. Those original style M60 turrets were then going to be mated to M48A3 hulls thus creating the M48A4.