starting up 340 that's been sitting for a few years

I would not start throwing parts at it. Do some investigating...I would try priming the engine 1st while turning the engine over by hand(spark plugs out). This will circulate the oil thru the engine.
Once you get er lubed up, crank engine over and verify points are opening/closing.
Chk plug wires to make sure they are hooked up properly.
Chk wires for spark
Verify you are getting fuel.
That's the order I would do it anyway...just my opinion.
Just because it doesn't start after sitting for years means you throw a elec ign at it.