That timing cover you have appears to be have the crank seal installed from outside. So i would say it's from the 80's. That makes it WAY easier to change seal if need be. Otherwise the timing cover has to be removed to change the seal.
For 69 covers the timing marks are on pass side. If you decide to you want 69 I have one listed for sale.
Congrats on the 340! You will have fun.