|Try gapping and cleaning the points. |
Gap the points with a CLEAN feeler gauge. Also, make sure they aren't binding on the pivot pin.
With points closed, pull a clean piece of white cardstock through them a few times to burnish them.
Then, turn the engine over 'til the points are open and hose them off with electrical contact cleaner and allow to air dry with them remaining open.
A sticky valve could also cause in intermittent miss. I'm sure you'll get lots of opinions as to what magic "Tiger Pee" is best to clean them up, so I'm NOT gonna go there!
Air filter is WIX 42302 (NAPA 2302).
A bad condensor is a REMOTE possibility. About ANY REAL autoparts store with an "associate" that's willing to grab the Ag and Industrial paper ignition parts catalog can get you a condensor, if it comes to trying that.