I was involved in an Argosy operation almost 20 years ago (2 x 200's; 1 x 100). They were a great concept - donks off two F-27's for three times the payload, but they weren't the best hot and high. Cairns - Port Moresby, 480 nm, 12,500 kg payload, but still struggling to get 12,000 feet at TOD. Loading and unloading was a dream.
I think in the end, reliability of the steam driven bits and electrics were their downfall.
They operated in Australia for many years; not sure where they ended up - maybe in New Zealand?