[THEFERMANATOR]

Here goes, according to the catalog the 50 uses it's own unique cylinder head and the 60 and 70 use the same head. The carbs are different for a 50, 60 or 70(figured this was the main difference), but the rest of the parts look to be the same. Even the exhaust tuner is the same part number for all 3. So if you have a 50 you'll need a 60/70 cylinder head and the bigger carbs with the correct jets for the bigger carbs. And possibly a different timing setting. So if you could find a cheap junk 70, you could swap a 50 to a 70 in a few hours time.