Open the track in mapsource, and save it as a standard garmin file (forget the extension). Then run it through gpsbabel to convert track to route.
Conversion works both ways.
I make all my routes using topo8 (Delorme). I then export it as a GPX and go through this processes with mapsource so I can hand both the route and track to Garmin users.
2014 R1200GS - My Naked Street Touring Bike
2000 KTM LC4 640 E - For everything else