I think you are asking as per the Vehicle Standards Bulletin 14 (VSB 14), National Code of Practice for Light Vehicle Construction and Modification (NCOP). Which is the code governing engine swaps. This is the link to the full code, then this is the relevant part re weight/capacity.
Incidentally SA (and I think maybe Tas?) hasn’t adopted this, which is good for me as I believe you guys cant put the 454 into a VR.