A cabinet sized 53" X 18.5" X 7.125" is about four cubic feet, outside dimensions, so the cabinet would be tuned lower if it used the same port. But you'd lose bass response because the cabinet would be be tuned too low to do much good.Assuming a few hundred cubic inches are displaced by components inside and by wood thickness, your cabinet is 3.5 cubic feet. So to tune this for 40Hz, you'll need to shorten the port to 5" long, assuming the same rectangular W x H dimensions of 3.5" x 6.0."
That will tune it to the same frequency as the "stock" Professional Series four π speaker, and it will sound pretty good. A 2226 works very well in cabinets from 2.0ft3 to 5.0ft3 tuned to 40Hz.