273 super commando #4 and #6 not firing

You are "sorta" on the right track but you should NOT just "pull" plug wires. This is because (if there is spark at that cylinder, and there should be) The spark voltage goes WAY up when one is removed, and looks for the "easiest path to ground", just like lightning

What this means is, that when you pull a wire, it just might "crossfire" to another cylinder, and confuse your results

The better way to do this is one of a number of ways:

Pull the boots up off the distributor, and if you have a small probe, ground each one by slipping the probe down beside the wire in the cap. If not, you can slip small brads/ nails down in each one before you start the engine.

If you have "guts" you can pull the wires out of the distributor, and then GROUND the distributor tower with a probe, before you make a decision.

Redfish was getting at "checking your wires." You can check spark at "each hole" by pulling a plug wire with insulated pliers, and then checking the spark to a grounded screwdriver, or pull them out of the distributor and let them arc to a grounded probe, held near the top of the tower

To check the wires without an ohmeter, once you identify suspect cylinders, ASSUME the wires and plugs are bad for that/ those cylinders.

SWITCH those "dead" wires with two other cylinders, and repeat your test. If the same cylinder(s) show "bad," it's not the wires.

Next, inspect the plugs on those holes, and either switch them with good ones, or replace with new ones, and repeat your test.

Some things to cause this:

Points worn so bad, that they are opening on only SOME of the cylinders, made worse by a worn distributor shaft/ bushings

Bad/ carbon tracked/ wet/ cracked distributor cap and or rotor

Bad plug wires OR plugs

Solid lifters that are too tight PAY ATTENTION THIS ENGINE SHOULD BE SOLID

Bad valves-- run compression check

Leaky, blown head gasket