I have had some of the same issues with GM 4.3 Liter engines. I’m on my 2nd one which has problems occasionally also. The first and second vehicle went thru feul pumps and power steering pumps. The first one had intermitent problems that cost me alot of money. I bought a new computer a NAPA and changed it myself. (easy).
My current one is a 1993 with a new engine at 125000 miles because of a head gasket. Had the same problem with the first. I like the vehicle for towing, the first was rear wheel drive the second is all wheel.
I don’t have a solution but will watch this subject closely.
My current vehicle a couple months ago (my wife drive it) the senario is get off work drive 2 miles to the gas station shut off the engine. It takes multiple try’s to restart. Drive normally for a week or two. Same problem. We switched vehicles. I drove it 4 days. Lots of short trips no problem. Stopped for gas same problem. After many many try’s it starts. She starts driving it again a week or to later short trip to the PO won’t start. She was across the street from Miller Chev. It started she dropped it off. The only thing they did was change the distributor cap and rotor. Ran fine for a month. Problem came back. Took it to Miller Chev left it for 3 days they tried to get it to fail and it wouldnt. I’ve been driving it for several weeks with multiple stops daily and its worked fine. Any suggestions would be appreciated.