It could be fuel. Some major things you need for an engine to run is compression, air, fuel, and spark. Did this thing have any kind of a miss? I don't think a clogged cat would keep it from running this long. the pressure would've blown out the seems by now. Try dissabling you fuel. Take out the coil wire from the center of the dizzy and hold it within a 1/4" of theblock. have someone crankit look for spark. That'll verfy for know whether or not it
is ignition related. If you can run a compression test. If all that is good go after fuel. See if their is air line fitting looking thing on your fuel rail. Turn the key on engine off you'll hear the fuel pump. while it is running press the center of the fitting. Like letting air outta a tire. if fuel spits out fuel is (superficially) OK up to the fuel rail. If all is still good go after the fuel injectors. Remove No.1. That's most likey to be the worst. Inspect it for obvious damage or corrosion. You could even take resistance readings at the terminals (but that's not the most dependable form of diag). If still nothing I would have to goe out there and see for myself.
PS- I hate giving tech advice