looking at purchasing a car that has had an engine conversion (nissan not honda - though thought with hondas this issue may be more common so posted here)

From what i have gathered the conversion requires an engineering certificate (pretty much 3 litre n/a converted to 2 litre turbo)

The seller is willing to sell with blueslip (car is out of rego and requires it - dont ask me how or who is doing the bluey as i have no idea)

but would there be any issues when i go to register at the rta?

i dont see how the turbo would cause any issues as the person at the rta prob wouldnt realise whether its turbo or n/a from the engine number but what about going from 3 litre > 2 litre?