Not sure there is a 55A alternator for the older vits.
40A or 75A I think thats your lot. the 75A drops right in and also has a spare pin, didnt give me any aggro till it toasted after being filled with crud.
Checl all your earths, check the earth strap to the battery and clean it on both ends. Its possible your battery is toast too, if its been mistreated, flattened jumped, run till flat, jumped... it may be damaged.
Checking with an ammeter wont tell you a lot. If the voltage is right its probobly all ok but if you are concerned you should take it to someone who can test it.
Its possible you have a short someplace, if this is the case its sinking arount the max output of the alternator, thats going to produce a hell of a lot of heat and will cause a fire if you arent careful. Also check you are getting a battery warning light when you turn the ignition on. Som alternators use the bulbe to provide the inital 'excitation' current.