Trying to figure out my brakes

The car has B51 on the fender tag and I am starting to think that it should probably have a booster on it, however I think that would make the problem worse. Does B51 come with booster?

The original owner said they at one time tried to switch the brakes over, but put it back because they were too gabby. I dismissed what he was saying because he really wasn't mechanically inclined. When I test drove the car they seemed touchy, but I didn't really try hard braking at the time (you know, beating up somewone elses stuff), but now I know I have to definetly sort something out

I am not against changing the system over and in the long run I know it would be the best way to go, but the car has really cool Cragers on it that are in really good shape and I want to keep those on the car. The car has the exact look I wanted (other than sagging in the back a little) and don't want to alter it too much anyway.

Thanks for all the advice and keep it coming!!