Like Jim said Bear, it probably is a 200.
I would feel better about it if it was one he had built.
That seller's name is Tom Schmidt, and is a reputable A/P mechanic in Ft Lauderdale.
Of course like any other engine builder, people will all have their own opinions of the man.
Most I know who have delt with him, are satisfied with his work.
I would say that if he had built it up from parts to be a 200, then it is.
He would know how to do it right.
Alot of people I know would want a "real 200", cause they believe a parts built one will usually fall short of the real thing from Lycoming.
Again, just peoples opinions I have heard.
Sounds like a take-off from an airboat that he did not build.
He may have been inside of it to inpect it. I just don't know.
If your really wanting a 200, I'd try talking to him about it.
Perhaps theres more to it than meets the eye.
It could be a good one, cause I have not heard anyone ever say that the man sells any Junk.