69 340 timing chain questions - help!!

Play with it!
Pull all the spark plugs to relieve all compression. Grab a socket and 1/2" pull bar and turn the engine in the diirection it runs. You'll see the timing marks go to where you set them up and back to where they are now. One reveloution of cam sproket is two revolutions of the crank sprocket.
or
Close it up and stop playing with it.