Looks like NSW HH-60H's have already switched to the M240:
And indeed the M60D is the correct name for the aircraft mounted M60, easy enough to tell apart as it has the same arse as the M2 with the two vertical hand grips, the M240 also has a version like this unsurprisingly called the M240D, as seen in the picture above.
The M60E3 is a lightened version of the original infantry M60 (seen in ofp), it was made to fix some of the major faults, however it didnt do its job very well, hence the switch over to the M240.