As long as the engine turns freely there should be no need to tear down the motor. Looks like a worthwhile effort. Too bad he tore the carbs completely apart since the PD carbs can be a bit of a challenge.
Good luck!
If "tear down" equates to complete rebuild, I agree. It may, depending on compression levels need a top end refresh. Assuming it turns freely, run a compression test. If compression levels are even and at nominal levels, then move on to looking at other things. Does it have signs of weeping/leaking gaskets or seals? Drain and inspect the oil and pull the pan off to look for any apparent glistening or metal bits that do not belong (indicating metal on metal wear, or shards from bearings or transmission gears).
Assuming you have good compression, no leaks, no apparent signs of internal metal wear, you might not need to crack the engine open.
