Please help me diagnose this 273

After the valve adjustment go around to the back of the car and put your hand over the exhaust pipe. The outgoing gasses should push your hand off continuously. If it feels like every once in a while your hand is getting sucked onto the pipe, that would indicate a faulty exhaust valve, and she needs either a valve job or a new spring.

Then after proving the firing order is correct, pull one wire off atta time. The one that either makes no difference, or runs smoother with out it, is the pesky cylinder. There may be more than one.
You also need to test for an intake leak, it may be that the replacement intake is leaking at the ports, or in the valley, or under the carb.

The rest is already covered except;
With electronic ignition, your pick-up needs to have one ORANGE wire on it.
If it has one gray wire, it is probably for a reverse-rotation engine. The proof is this. you can adjust the timing to a number (below the rpm at which the D starts advancing). And it will idle just fine. But as soon as you try to increase the rpm, that backwards polarity pick-up, will start randomly dropping sparks, and spark anywhere it feels like; either retarded or advanced; it's just a mess. If you see that, you need a different pick-up.