Hey. You didnt hear it from me but, All you need to do is hop into vicroads and tell them
"My engine exploded i have replaced the engine new number is (##103KW##)" They will update your details, because your engine number has definately changed, As long as the new engine number starts with 4a there should be no problems, This isnt as easy with poor ke70 guys with the 4k.
Enjoy.