Best Source for a Replacement Kawasaki Engine

I tried rebuilding one of those oil leaking FH580V engines. It was in pretty bad shape but I gave a shot at rebuilding it since that option was much cheaper. Well, after about 25 hours on the rebuild it is not holding up very well. I havent even bothered to check the compression, but Im pretty certain thats the problem.

My question is, do any of you have experience buying a replacement Kawasaki engine and can recommend a good source? I have found several companies on line such as...

Best Source for a Replacement Kawasaki Engine