I have converted several pipes to use a Dr. Grabow or Medico type filter. Smoking a Brigham as I type that I converted to use the 6MM filters--didn't care for the Brigham wooden filters. If the tenon is large enough it can be drilled out to accept a filter,but usually the shank will need to be drilled also. I have also removed the aluminum tenon from Dr. G. stems and put them in other stems to replaced a chewed or broken stem in a DG,that can involve quite a bit of work in reshaping the stem to match the shank.Also have to make sure there is enough length in the shank and stem to accommodate the filter.
Might be easier to just buy filtered pipes. All of the Dr. Grabows produced today use filters as do Medicos(they are still making Medicos right?) Many of the older estate Grabows do not take a filter. As I mentioned the Brighams use a wooden filter,and several lines of pipes from Europe use filter although the are mostly 9mm I think.Others can tell you more about them.