. . . What happens when the fancy system [proprietary system like Pertronix] craps out 50 miles from nowhere, and all there is in the way of parts is a local jobber? . . .
What might happen if a non-proprietary (?) conversion system craps out? You'd be at the mercy of finding an open local jobber, with someone able to look up parts, having the correct part number in a book, and having the correct part in stock.
That would also be a quite possible problem.
I take a much more practical route with my "risky" Pertronix "fancy system". I carry an "insurance policy" (which has a one-time cost of about $100) - a spare (tested) distributor with new condenser, cap, and points (set and ready to go). This $100 insurance has worked well for me for two trucks for about 15 years (even though the risky, fancy, Pertronix systems have not failed). Nonetheless, I could change the distributor in about the same amount of time that I can change and set a replacement set of points.
One important consideration when using Pertronix (or any other fancy electronic system): be sure ALL your electrical connections and grounds are good. If they are not good, you could burn out a sensitive electronic (solid-state) part and or have intermittent misses/problems.
