I had my Midland Hy-Power vacuum booster rebuilt by Ed Strain who is located in FL. He has been bought by White Post but Ed still does the work. I was very happy with the rebuilt and discussions I had with him. He does the Treadle-Vac units too.
https://brakeboosterrebuild.com/abou...ild.com/about/
https://brakeboosterrebuild.com/identification/
Glenn