All they are is a SA-200 with a Yanmar 4TNE88 engine in it.  My brother took his in and had it converted two years ago and loves it.  It only uses about 3-4 gallons a day.  They took it completely apart and went through every thing and maid it like brand new.  He went to American Welding Supply in Groves, Texas and I think the bill was around 6K but don't quote me.

I ordered one January and was told last week that he hasn't worked on any in the last month, and didn't know when he would get back to work on them.