How do identify what year my engine is?

Thanks for the photos and observations. So I need to adjust the arm forward more until the end of the slot is forward enough to be making contact with the pin that goes through it?
I have no idea what arm is on it. That’s why I hate it when people monkey with things instead of leaving them stock. The car is exactly as I bought it. It was originally a 273 car. The trans does shift into all three gears. It just shifts very fast and is in third before you know it.