The 716819 is the engine block serial number - no connection to the VIN. They didn't stamp the VIN on the block between 1964-67, so 2+2's of those years don't have a VIN on the engine.
Check the casting number on the rear of the block, adjacent to the distributor hole -
Click here for link to Wallace Racing's excellent explanation & photo's on ID'ing Pontiac engines.That will tell you the date it was cast, which should be roughly a month before the car's assembly date. If the casting date seems correct, it's most likely the original engine.
As for the transmission, the VIN is stamped on the top of the case on a Muncie transmission. Unfortunately you need to drop the trannie to see it, unless a good mirror will fit well enough - I've not tried that. As for an auomatic, I don't know if that has a VIN stamping.