1986 GMC Sierra Engine will not start

Engine Performance problem
1986 GMC Sierra 6 cyl Two Wheel Drive Manual +100K miles

Engine stopped working while running twice. Both times waiting about 10 to 15 minutes it started and ran fine for some time. A major repair was done weeks earlier replacing engine timing chain. The third time it did stopped similarly while running but this time it never started again. It happenened about a year and half ago, I towed the truck back to my garage and simpley left it there recharging battery from time to time with a charger. I need the truckk now and thinking the symptoms resembled electronic ignition module failure, I replaced it yesterday and recharged battery. I tried today and it did not start after carnaking for a while. Checked spark plug #1 for sparkland non was detected. Looked for the coil to test but did not find it or at least did not recognize it for my year model u nit. It is a GMC 1986, 4.3 liter, four barrel carb and manual tranny. What else could be the problem other than the module?
Replaced distibutor cables and cap about four years ago so they are not too old.

Thanks in advance for your help. Tony