The engine is identical to the 50sxh in all but 2 things.
1. the head, improved cooling and it looks neat, same combustion chamber and compression ratio.
2. bigger throat carb, that means more fuel which means more power.

Of those two the biggest difference is the carb.

It wont run without a head but if you have a standard 50sxh head it will fit and run just fine, I'd just run it a click or two richer.