Well, it's a Sportster for sure. Sportster pushrod tubes are nearly parallel to each other, running each to their own cam. Big Twins have a single cam, so all the pushrod tubes converge on that point. Not a Big Twin so you wouldn't call it a Panhead, Shovelhead nor Evolution. I'm guessing a '70s vintage by the square-section swingarm and shocks mounted way back at the axle area.
Other stuff (seat, tank, forks, wheels, etc) are too easy to change to rely on 'em for year clues.
Someone'll know, though...