Not exactly sure but I think the Helitrans S58T's were PNG registered. I was at the Turama River base in PNG mid 70's and seem to remember that they had 2 x S58T models and one S58 C model there contracted to Oilsearch (bit foggy on the number of machines). They must have been able to carry passengers because they used them for crew changes as well as slinging drill rigs and heavy equipment around. The C model was very rarely flown or didnt fly much when I was there anyway. They had some Jetrangers and a Lama there as well, some of which were Australian registered. Must have been around the time of PNG indepence with the mix of PNG and Oz registered machines!
Wally Watkins, Wayne Knight, Rick Howell, Blair Weaver, Tony Silver are some of the names that come to mind. Peter Manktello was there as well in the early days! There were others but I can't remember them all. I owe a debt of gratitude to those Helitrans guys at Turama River who inspired and encouraged me to go on and get my helicopter licence that led to a great career that I would'nt have changed for anything.