Any 1P-series Borg Warner transmission converter should work whether its Ford-O or Merc-O-Matic. 1951 through 1953. I'm not sure about the 1954 with early Y-blocks but I think they were similar enough. Other than a half dozen older salvage yards around the country, Flea-Pay or C-List may be possibilities. Check with Fred at Southside Obsolete too. Owens Salvage here in Texas has a lot of old stuff. Other yards may be listed in Hemmings. The EFV8 club has listings for auto trans parts some times and so does Hemmings. Those old air cooled units are still out there if you know where to search.