First, let me assure you that even if you use single product HTML code, its still has that <script…> line. So the methods of custom translation for it are the same, unless you need to change something that is already written literally inside that HTML code - in such case you only need to change that text in HTML code.
Unfortunately, it is not possible to change the names of the carrier calculated shipping methods (like the ones coming from Australia Post).
Carrier calculated shipping methods in Ecwid work like this: when a customer comes to checkout page with an order that requires shipping, Ecwid requests each carrier's site according to your settings to provide the rates for this order and customer's destination. Once the carrier site respond with the rates, Ecwid shows them without any changes. The method names are also a part of that information, so unfortunately it is not possible to change that.
If you would use the user-defined shipping methods, you could easily change their names the way you like.
If you would like to have a way to change the displayed names of carrier-calculated shipping, please, submit your idea to
http://ideas.ecwid.com so we could consider implementing it in the future version of Ecwid.