Esteban, yes my unit was credited with the first Russian-built tank kills of the war. We knocked out dozens of them at An Loc. We used 11 lb. HEAT rockets in our 2.75" rocket pods to do the job. Cobras also had 20mm Vulcan canons on the wing with AP rounds that did an excellent job.
The American tankers had all been pull out of Vietnam at this point of the war and while the ARVN's had 48's I'm not aware that they ever engaged any of the NVA tanks. They all pretty much dropped their guns and ran home to mommasan during this offensive.
The AC-130's Spectre gunships were especially effective against the tanks. U.S. TAC Air was also all over them with their bombs.
At An Loc the chief adviser on the ground, Col. Bill Miller convinced the ARVN that the M-72 LAW would also do the trick by going out of his bunker and shooting some of them. Here's a picture of the rearend of one of those T-54's with Col. Miller standing next to it.