When they have multiple listings like that... it's generally either a color change... or a different region code. (like USA, Canada, export) Don't know why they did that, since they are generally the same.
Sorry no one has been answering your questions... but no... don't try to just to the top. It's an old engine, and the lower is warn out too. If you have a machine shop available to you... then sure... you can try to do the rebuild yourself. But, it's cheaper to just buy a SBT engine... and you will have a warranty when you are done.