Are you using an otherwise stock ignition or has it been "augmented" in some way?
That is when it was 100% stock. From day one it had to have a cap and rotor atleast once a year. It was done under GM factory warranty 3 times. Once by the original owner. The wires only lasted 2-3 years before they were cooked as well. 105K mile first tuneup, not a chance.
I had a 24x system on the 350, but as I learned these vans eat LS coils. Even the stock LS vans do. Got tired of having to change 1 after another from heat related failure. My coils were used ones that I initially put on it, but once 2 of the Delco replacements failed and I built the 383, I put the single coil/distributor back on it. I now carry a spare coil and module already on a mounting bracket with me along with a used cap and rotor. In that box is also a used thermostat and a used crank sensor. Those are the highest failure items on these trucks.
Currently I am running the same United Motor Products aluminum distributor, the same old MSD cap and rotor and the same old Davis Unified Module and Coil that were on the 350 for more than 3 years before I put the 24x on it. The Taylor wires were new for the 383. The distributor was run sans cap and rotor with an aluminum housing cap on top when I was 24x.