Wasn't the original mod of the NT-37 completed by 1967? Basically just a Mk37 with Otto fuel engine... effective range of 15,000y at 36knt. If that thing was available I wouldn't even consider the Mk45. In a "SHTF" cold war gone hot scenario such a weapon (or field mods) would likely be fast-tracked if it was deemed that current weapons were behind the curve.
Website with some decent info on post-ww2 US torps:
http://www.navweaps.com/Weapons/WTUS_PostWWII.php
EDIT: Scratch that, just found documentation stating that the Mk37 was being tested with the otto fuel engine in 1968... so at the start of the in-game 1968 campaign it wouldn't have even come close to deployment even with rising tensions pushing development.