I bought an engine replacement kit from Small Engine Warehouse a few years ago. There was a slightly smaller Kawasaki engine, a mounting bracket, and the variable speed pulley that goes on the engine shaft.
The price was good and it was a pretty straightforward job to install. It requires a moderate amount of cursing to get the engine under the frame until the mounting bolts drop into the proper slots. The throttle, choke and fuel connections were simple and obvious.
I remember there being a question about electrical hookup that required a call to Small Engine Warehouse, but they gave me a clear answer and I didn't have to change any wiring or connectors.
It is a smaller HP engine, but the performance is very reasonable.