if it was defected and never inspected at dickson, the system will not let them issue rego without an inspection by dickson. taking it elsewhere is a waste of time and money.
If its nice and quiet and the engine bay looks stock take it over dickson and see what they find, they get one go at checking it for problems, once you have fixed/engineered what they find they cant then complain about other things, if they do try to pull that file an official complaint/dispute. The people at the shop front can tell you who you need to speak with to do that.