There used to be a C320 (Skyknight) VH-DRK doing survey work in those times, unsure of the cloud seeding though.
It was in a sorry state for a long time in the GAM graveyard at Essendon.
Not sure what happened to it, but it definitely didn't fly out.
As a matter of interest, what was the difference between the 310 and 320,
apart from 10 in case those of you wish to state the bleedin' obvious?