I would rebuild the master cylinder about every 2 - 3 years. Thats What I HAVE to do on my 1958 because its a single piston system that has really no safety in it.
So the plunger and spring from that kit did not fit the stock housing. I cleaned the old parts and put them back in and bled with new fluid. Put 300 miles on it last weekend and it worked great. Laconia was awesome.