Well there is more to it than just suspension, but I can't answer the "post registration" question. I'm sure you could get it engineered, but that costs money.
Not according to 3 people i know on Eoz that had it done on cruisers..
It's a complete suspension kit, then testing - For Lucy and his troopy - all of the testing was braking, and hand brake. But they had the data from someone else, so he didnt have to pay the huge $$$$
The only way to get it done is to hire a race track, professional driver and more (total cost $10k+.. if it fails, rebook and pay another $10k+) Then that data can be used by other people (as above)... but the data is only good for someone else only with the exact same make/mode/engine/gearbox/tyres/weight/younameit car...
Must be same engine (TD is different to TD IC), same suspension same gearbox etc. The big issue we had at the time was finding tyres that would be legal then.
You can see what needs to be done in the first link above on patrol forum..
I went into it with 4 different Vicroads engineers... None would touch it once car was registered..
Spoke with TJM/ARB/Lovells and then Ateco at the time, they were too busy doing a kit for the 200 series at the time, and weren't interested.
Make the process easy and cheap and everyone will do it. Its not hard.