I'm with Bartamos. Why rebuild the engine? If it's running and doesn't have significant problems, just clean it up and fix oil leaks if necessary.
On my project, the engine ran when I got it and sounded good. It had a few serious leaks, such as the timing cover seal, which prompted me to fix that and replace a few other gaskets. I did pull the rocker assembly off for cleanup and inspection, which led to the discovery of a bad lifter (upper section loose from the body), so replaced that. It got a fresh paint job, and that's about it. If it gives me trouble later, that will be fixed as needed. I expect it will last me for the rest of my life.
