Welcome to the forum, before buying a engine take a look at this thread.
As far as the bike you are looking at, just like all bikes, the most important thing about mounting a engine is the degree of the mounting tubes. For optimum fit you want to work with a 75 degree angle. You want the engine mounts to be flush with both tubes. This can be accomplished with a shim on straight tubes to a custom mount for curved tubes such as that on a cruiser. Also shy away from drilling holes in the tubes.
Here are some pictures of engine mounting you might want to review.
Engine Mounting pictures by Ron-Becker - Photobucket
The bike you are looking at appears to have a 60 degree "V". Blew up the photo and measured with a protractor (http://www.ossmann.com/protractor/
). The engine will have to be mounted higher and a custom mount made. That's my .02 for whats it worth....