Ukraine has Challenger 2s and Abrams now, plus Leopard 2s. Ask Iraq how that worked out.
This is like the UK pulling Centurions out of storage and sending them into action.
But even the 105mm L7 gun from 1958 (used on the Centurion Mk 5, M-60 and Leopard 1) was specifically designed to take out a T-54/55.