I had a Powermaster XS starter for over 10 years and started to have problems this spring. I had beat the hell out of it and used it when I had a bad ground and pulling excessive amps so none of this was the starters problem. I noticed on the web site Powermaster offers "factory refurbish" service. I called them up ( I only live about 15 minutes from their plant that is in West Chicago, IL) and told me I could drop it off so I did. I told them to call me if cost would be over $100. This was about 3 in the afternoon. The next morning Powermaster called and said it was ready! Cost was $80 and they replaced the case, solenoid, and Bendix. I picked it up and it is working great.
You might want to contact Powermaster and see about getting your old XS refurbished just to have a spare or to resell.
64 Galaxie NSS