The clutch cover will work, if you are referring to the entire assembly. There are differences through the years on the components that make it up. The 55 top cover will not work on the 50 unless you change other parts. The other parts are the carb and choke. The air filter and base are different, so you can swap from the 55. The tank is a little different on the 50 because the trigger has the fast idle catch. The 55 uses an eccentric on the choke to set the fast idle. There may be a difference in the throttle rod, don't remember for sure. The 50 top cover has the choke control. It pushes down on the air filter to choke it. The 55 upgrade is a good way to go, easier starting. I'd recommend using the 55 air filter with a screw in the center. I don't know anything about the 154, but the 44 parts won't fit it. The 44 has a one bolt clutch cover and completely different air filter, choke, carb set up.
