The HW-16 has a 2-pole crystal filter. The CW filter from HW/SB-X0X line will work. HW-16 BFO frequency will need a little adjustment if you don't have the crystal from the HW/SB-X0X. Make sure the filter you install works before going through the trouble. You won't get as much signal through as with the original and the HW-16 is already a little weak on 15m receive. Couple the filter with some .05 or so caps. Drill some small holes and it mounts on the chassis between the dial and the printed circuit board. I'm not sure I like the 4 pole as much as the 2 pole that's original. In hindsight, I should have added a switch, a variable frequency BFO, and maybe a solid state gain stage before or after the filter. If I ever get around to putting it back on the bench, it will get an adjustable load control and if I can find a crystal...20 meters instead of 15.
73, -Bob ah7i/w4