I do not believe there is any such thing as a complete rebuild kit available anywhere.
A rebuild involves many variables. Each engine is different, has different amounts of wear and/or damage.
If the rod bearings are still good you certainly do not want to open that can of worms.
If the bores are worn, what is the amount of wear?
Has the engine been bored before?
Everything has to be checked and measured to determine what is needed and what is fine and will continue to run without problems.
Any engine with considerable miles on it will also have issues with the clutch and possibly the transmission in addition to the engine.
It would be nice to have such a kit available, but it would certainly not be practical.
Rolling down the highway on two wheels since 1957...
Owner Red/White 1971 XLCH & 2003 FXDL-Silver over Black