Indeed ... I tend to be a tad loose with these things ... to me a Nav is a Nav regardless (for flying purposes) although the Chieftain is a bit more fun to fly in my view.
Point of the question is that I haven't come across a 350T so wondering what it is ? Generally, in Oz, a minor nomenclature change indicates a local STC type modification ... just a minor point of interest for me.
Basic definitions are as per
TCDS (A20SO).