http://www.mallardaircraft.com/
A new development from Frakes Aviation, the current owner of the model G-73 type certificate (A-783) and the first STC to install PT6A turbines on Mallards (presumably the different turbine engine installations used by Paspaley Pearls in Australia is approved by some other means through CASA "down under".)
Funny thing though, they (Mallard Aircraft aka Frakes) is claiming that Frakes "later purchased the type certificate for the Mallard and incorporated the turbine STC into the type certification." While jsut about everybody already knows that Frakes bought the TC from Grumman, there is absolutely nothing in that TC that mentions or in any other way references the turbine engine mod. It appears from the TC itself that the only fully TC'd configuration for a Mallard continues to be with the 600 hp R-1340 radial engines. The "Frakes" turbine engine mod for the G-73 series seems to remain only an "aftermarket" modification per STC SA2323NM as opposed to a fully TC'd OEM / production feature, etc.