Smolony,
I have a 50 3100 and there were no holes in the backing plate for the shoe hold down keeper and spring assembly (like what comes on Bendix style brakes). I have a 49 that has a piece of sheet metal with a hole in it that comes off the backing plate to accept a spring retainer that has a hook on the end of it. (The 50 does not have this sheet metal with the hole in it). I don't know what you, or I are supposed to have on a 50 3100. I am just telling you what I have. I'm sure someone else here can let us know.
