No mention then of a possible engine retrofit. It would seem logical to pursue the chance of a 30-40% reduction in fuel burn on airframes with so many cycles/hours left.
Some years ago there was speculation of the RB 715 and Pratt PW6000 as potential candidates. The PW weighing in quite close to the original weight of the JT8D-219 and less than the RB 715 but with higher max thrust.