RVAC at Moorabbin has been ordering exchange new/overhauled Lycoming engines thru Aviall, with the updated stronger cases & roller rockers, and returning their old cores. Its been cheaper and quicker doing it that way, and Aviall at Moorabbin are the ones to speak to regarding it all.
They probably did it due to the dollar being equal a while ago, but have exchanged quite a few in their fleet now. No old AD's and modern parts guareenteed. ... just so whatever is viable at time i reckon...
ut quicker to get overhauled, if there are parts available