Conway-
I highly suggest you hire a DAR and explain your idea. Be sure and tell him about the upcoming SID in the near future. Pull up a chair and have a Video Recorder handy to record his reaction and the estimation of the cost entailed with obtaining a COA in AU. After this meeting retire to the nearest Adult beverage establishment and calculator in hand tally up some estimated cost to bring aircraft in Conformity. I see from your website that you have operations with NSW Rural Fire Service. Call these fellows up or someone within CASA and obtain some information concerning importation of a C337 for Commercial use. C337's are a perfect platform for many useful purposes Commercially. Unfortunately the FAA is about to place very large financial cost upon Commercial operators using Service Difficulty Reports as a basis for a Super AD for Part 135 aircraft and foreign operated 337's. This SID will be mandatory for foreign registered aircraft if the Cessna recommended maintenance is required. In addition I believe to obtain a CASA COA the Cessna Time/Calender life items must be satisfied. Replacement of the Hyd hoses,Pitot Static tubing, Engine Control Cables (@TBO),......and many more items. This list doesn't include the Super AD (SID) issue. When the Super AD (SID) becomes law the inspection list will grow considerably. Please purchase a C337 service manual. Here is one for 1964-1974 337's on CD. If you do decide to go forward with a Skymaster purchase wait till after the SID is released. This document could affect the price of a aircraft significantly, especially outside the USA. There should be a majority of C337 operators unloading their aircraft. Then you can perform the Super AD (SID). The Directors at CASA and the Aging Aircraft Directorate Department of the FAA, could make you a example of a inter governmental cooperative effort example. Demonstrating a marriage of industry and Governmental Regulation making the skies safer. But unfortunately for your company's financials this will only last 10 years, even if the plane is stored in a hermetically controlled environment with minmum flight time accrued. You will be required to repeat the Super AD (SID). Along with the Cessna mandatory time/calender limits which exist presently. BTW Louisiana Tech has a very nice HUET setup in Lafayette, Louisiana. Very nice and knowledgeable instructors well equipped and a worthwhile course as you know if you fly/ride over water in flying machines.
http://www.mccurtaintg.com/cessna3.htm#sku33701