mounting can settle one. as long the cc is within the 'legal' range and cleared by bahagian teknik. coz checking is done at puspakom and if u ask runner to bring in, u can clear quite easily at puspakom.
i've seen b18c gsr mated with b20b bottom get cleared. they dont have expert to determine these things. there's so many manufacturers od cars and no one have the time to study them all, at least at jpj or puspakom....hehehehe