Help me build my 340

Like Rusty said, the 71 340 is quite a formidable package--and that was out of the factory with all the potential inequities. If you put everything in the build the way it's spec'd to be, it'll perform very well. Blueprinting and proper application of parts within the package make reliable power and performance.

If you want to, and the engine needs it, then sure-rebuild it. But if your compression is good across the board, doesn't consume or leak oil, make weird noises, and it runs well after a decent tune up session (timing and carb adjustments), I'd just run it as is until such time that you need to rebuild it.