Before you do anything check this, if it has a timing pointer set the dampner on it take the distributor cap of and rotate the engine back and fort to the point where the rotor moves barely either way read how many cranckshaft degrees it takes to do this, more than 10 degrees it needs a timing chain anything less you are still ok. This works for v8's cannot see why it would not be true for a straight 6, seems to me Jeep is the only one with timing chains for their line engines