I thought about it some more. The engine might not need engineering, but I would suspect that the new engine mounts probably will?
The engine number will pick up on the rego when you change it.
The turbo and intercooler mods will need engineering if the specific engine number does not reflect the digits of these add-ons?
ie: if you change from a non turbo td42 to a later model factory td42ti you prob not need mod plate?
different rules for each state, but the ADR carries across so tehre may be somethign in there you can read up on?
if not, just ring transport authority - they will usually be happy to answer your questions.
Owen.