Kushil, most mobile RWC guys are pretty relaxed avbout things like that. The only issue you may have is when the car is inspected by Queensland Transport when you go to get it registered. They check over the car and make sure engine numbers/etc are the same as on the forms.
Having said that, The woman that looked over my Stag when I first got it rego'ed didn't know where the engine number on an RB was!