Call your local Vehicle Standards hotline. The number here in SA is 1800 882 248, I'm not sure if it's a national number or not. Talk to them about it, be polite and patient and listen to what they have to say even if they go off on a tangent.
I was nice and patient with a bloke here who initially said I could not get my twincam engineered with an aftermarket ECU, then later came around once I'd explained it to him properly
I'd only have to have a visual inspection to confirm the engine mountings etc are safe, have the engine number sighted, have a basic exhaust gas test (the cheap $80 kind) and some cheap stamp duty for engine number change and that's all, and that's with aftermarket ECU!

Twincam needs: surge tank, EFI lines, TPS, recored radiator, hoses, assemble the ECU (50% done).