I don't think it is possible to do that (at least not correctly). You probalby should have not moved your level to a completely different engine, at least not without backing it up.
SMBX Galaxy forum by Pivot40Channel http://smbxgalaxy.prophpbb.com/
Come to the SMBX+ forums by illias3000. There is a whole forum category dedicated to the boss rush series with official rushes, submit bosses, and fan boss rushes! It is still open but AirSeus Forums is now open: http://nsmbx.prophpbb.com/
AirSeus Forums the new home of the Boss Rush series: http://smbxairseusforums.prophpbb.com/