Im looking at that and making my mind up that the best way to deal with that enclosure would be:
A- Seal up the existing port
B- Convert to an Aero-Ported enclosure
Thats just me..you can get it tuned the way that youd like by doing an Aero-Port.
Im sure others may have a different opinion.
i think you can possibly utilize the enclosure provided the sub fits and possibly tune yourself by doing an Aero=Port.