"u sure can the internal size is 2.4cf seems to be turned to 20hzish"
shine a light in the port. the cab is 21" deep. if the port doesn't bend, that limits the depth of the tuning to about 25hz or maybe a hair lower in an enclosure of that volume with a 4" port.
i suspect that e.d. calls it "room tuning" instead of "enclosure tuning" because they are cheating, just like paradigm.
depending on what will fit in the cutout, the alpine swr-1243d, jbl w12gti, or the tcsounds epic12 will work fine in that cabinet. All are very good drivers. With 300 watts and a 2nd order highpass around 20hz, none of them will be anywhere close to their thermal or excursion limits and all will perform within a db or so of each other.