Aftermarket parts and RWC questions

Hi there, so I am looking at buying an MR2 very soon and I have a few questions regarding getting a RWC (first car in Australia for me).
What aftermarket parts would make it fail from getting a RWC? I am looking both in the ACT and outside the ACT, and obviously if I bring an interstate MR2 I will need to get a RWC and I want to make sure I don't end up buying a car that I can't register without having to buy a bunch of stock parts for it.
 
For example:
CT20b turbo = even if it works perfectly, would I fail the RWC because I need an engineer certificate for it?
18" rims = 3" bigger than stock, therefore cannot pass even if overall diameter is less than 7% different?
Aftermarket struts and/or coilovers?
Lowering the car?
I was also looking at a car with an engine swap: gen 4 motors from a toyota caldina?
 
I don't know who to ask so I hope I can get some help here.
Thanks!

hi alex the rules in act have changed and i think any imports have to go through dickson motor registry. wheels are based on the rolling diameter so with the right tire size you can have 18s. Coilovers are no good (apparently if you weld the adjusters they will let you have them) in regards to turbos the main thing they worry about is emissions so factory ecu, cat converter airbox blow off valve are the main things they will look for. The trade off in the act is that once you have rego you dont have yearly inspections.and unless you get a defect for.something obvious you can do what you want once you get rego. so look for a car with limited.mods or one that can be returned to stock easliy

the 25mm measurement is the cars track,measured from centre of tyre to centre of opposite tyre it relates more to your offset rather than tyre width it becomes an issue with modified diffs im not sure if you could fit wheels under the mr2 that could be that far out

Springs should be fine as long as you maintain the minimum ride height of 100mm (or whatever it is these days), and that your nothing fouls your suspension/body at the extremities (e.g. bottoming out).

Hi Alex,
The Hi flow cat passed in Adelaide, here they only check to see that it is heating to the required temp, to ensure it is working / doing its job and hasn't been gutted.