Place your bets...
Ross,
Maybe your buddy will have no vibration problems at all...
AT THE VERY LEAST, inspect it and ensure that the flexplate hasn't had additional material added to it or removed from it. The removed material will look like a series of dime shaped lesions that are cut into the surface of the ring gear in order to remove metal. If the flexplate is virgin, then a neutral balance flywheel should work OK without creating additional vibration headaches for you
The driveshafts are different length. So, if you can get the one out of that '67
TAKE IT WITH YOU
Crossmember geometeries are different also. You need that too and YES it is interchangable.
That low horse 327 crank may or may not have a machined provision in it for a pilot bushing, Im not sure. If it doesnt, then the engine is going to have to come appart anyways. If your buddy side steps this issue, then tell him not to complain to you about the 'chatter' he gets every time he lets out the clutch in first gear.
AND You may also want to double check that 327 block to ensure that it has a good stud boss for the "Z" shaft ball to screw into.
Like with all car related things, its the little things that can get ya!
Rock