learn "manual Qt", it is a very useful skill
just open the project in Qt Creator (it is using qmake/ cmake, right?) and see how it works. Qt is source compatible between versions, and Qt Creator can handle all Qt4 and Qt5 projects, so it should work fine
50 files does not sound like much. If you really want/ need to, you can probably refactor the project to make it work as you like with QtC