In IDR 12/1984 it is mentioned that the FOG-M or Hellfire follow-on could be a viable alternative to a gun MPGS.
Rather than procuring a new weapon platform, it was suggested that existing M113 APCs, M2 Bradley IFVs, M48 tanks and Humvees could be converted to that role.
Interestingly apart from the M48 it seems that all of those were eventually prototyped or at least drawn up in the form of the Ground Launched Hellfire – Heavy and the Ground Launched Hellfire – Light respectively.
https://www.google.com/books/edition/Hearings_on_Military_Posture_and_H_R_506/PqMfAAAAMAAJHearings on Military Posture and H.R. 5068 (H.R. 5970), Department of Defense Authorization for Appropriations for Fiscal Year 1978, Before the Committee on Armed Services, House of Representatives, Ninety-fifth Congress, First Session ...: Procurement of aircraft, missiles, tracked combat vehicles, torpedoes, and other weapons, title I
And here is a description of what it would take to basically put the Abrams' AGT-1500 powerplant as is into the M60 tank.
https://www.google.com/books/edition/Department_of_Defense_appropriations_for/nIW5hPRRtfUCDepartment of Defense appropriations for 1978
hearings before a subcommittee of the Committee on Appropriations, House of Representatives, Ninety-fifth Congress, first session ...
Also first time hearing about a stretched version of the M48 hull used in connection with the M103 heavy tank.
Would be great to have more info about that or even pics. I don't remember hearing anything about it in Hunnicutts Firepower: A History of the American Heavy Tank.
His Patton book probably doesn't contain anything about it as well. But It'd be great to find out it actually does...
https://www.google.com/books/edition/Department_of_Defense_appropriations_for/jVq2AAAAIAAJDepartment of Defense Appropriations for 1983
Hearings Before a Subcommittee of the Committee on Appropriations, House of Representatives, Ninety-seventh Congress, Second Session
And here we have information about a supposed 1980 Army plan to convert M60A2 tanks into M48A5E1 tanks.
Alternative proposals were made to convert them into AVLBs, CEVs or countermine/COVs.