My posts over the last several pages are headed a specific direction, although that may not be readily apparent. Unfortunately, I keep getting sidetracked, here and in real life. So ...
A complete list of ignition system components in our older Dodge motorhomes is ignition switch, ballast resistor, coil, ICM, distributor, high tension wires, and spark plugs.
Chrysler, along with other manufacturers, started throwing in lots of extra doodads in an effort to satisfy government regulations. But that list is basically it for engines made prior to the early '80s.
Add 12VDC wires and connections and you have everything that could cause your ignition system to malfunction, act up, or otherwise not work well.
12VDC wires and connections are significant. If they're not up to snuff, they could cause components to act wonky when the components are otherwise fine. I've already mention one example of this, in the form of swapped primary wires on the coil. Likewise, loose/dirty/corroded connections will cause intermittent or insufficient current, making it seem like components are failing. While much less common, older wires can cause problems if they're corroded, have broken stands internally, or suffer deteriorating insulation.
Ignition switches are largely mechanical and will wear out over time and use. Being small and inexpensive, carrying a spare ignition switch is an option. (The switch is easy to replace if it's mounted in the dash ... if mounted on the steering column, it involves a bit more difficulty.) However, it's easy to 'hot wire' the ignition so the choice is yours. (Identifying which wires are which provides most of the difficulty.)
I hot wired my '49 Int'l Metro for weeks so I could use it while manufacturing a new sheet metal dash. (The wires were hidden under an old couch cushion on the doghouse.) I twisted the stripped (bare) ends of the BATT, ACC, and IGN wires together and touched the START wire to that cluster to start it. The first three stayed twisted together while I was driving it and I pulled the bundle apart to stop the engine.
We've already discussed the ballast resistor extensively and consensus is you should carry a spare. Like the ignition switch, the resistor is small, inexpensive, and much easier to replace. More importantly, it either works or doesn't -- no middle ground. (Ignition switch tend to signal pending failure by working intermittently.)
In a pinch, if you don't have a spare ballast resistor, you can bypass a failed one. (Jump across the terminals or pull the connectors off and clamp them together.) However, I generally recommend against doing so, limiting it to getting out of remote areas ... with as little time and distance as possible. (To get to cell phone coverage or a land line instead of a part store or repair shop.)
As noted, a spare coil is an option but will probably never be needed. (I know first hand of a fifty plus year old coil working just fine for well over a hundred thousand miles.)
Spare distributor cap and rotor is a good idea. (Do like I do and save the old ones when replaced during routine maintenance.)
If you want to go 'all out,' a spare distributor reluctor and brass gap gauge is a possibility but also probably unnecessary.
Beyond spare cap and rotor (and maybe reluctor), there's not much you can do about a failed distributor without access to a shop and timing light. (I can time an engine by ear but it's difficult to do without lots of practice ... and afterwards I tend to verify with a timing light.)
Spare spark plugs and high tension wires are a final possibility. However, a problem there tends cause reduced performance rather than complete failure, allowing you to get to a better place for making repairs.
All of this becomes much less necessary if you fix issues before they become a problem. Along with regular good maintenance, judicious rehabilitating/refurbishing is advisable on older vehicles.
