Electrical/mechanical shutdown?

I have the car listed above fr 3.4l with 160,500 miles on the body. I’ve replaced the motor like complete replaced crank rods pistons heads polished ported new push rods all new sensors and accessories like p/s pump alternator etc, I also ordered a VIN specific ECM from flag ship after getting it running it began to automatically die in say about 10min then wouldn’t start for two hours. This was in the middle of winter as well so I’m sure it wasn’t getting hot, and the HVAC wasn’t on. Okay so every fuse that is accessible has been replaced as well as the relays. So, I got it to run for 15 minutes and figured it just needed to sync together. After two weeks I got it to run for two hours three times consecutively then as soon as I took it on the highway 10 minutes into it shuts off. Then when I got it home it ran just fine for a while when it died I could hear fuel pump and sensors clicking no lights on dash except o2sensor Dtc. Check spark nothing then I disconnected battery ECM BCM and removed and replaced all fuses under hood and interior. When I replaced everything, it started just fine again and shut off 15 minutes later. Like I said no codes but o2 sensor and it’s been replaced now so that’s gone as well. Now this week the battery light is coming on and oil level light, but oil is full and a new alternator too. Saying a generator problem on the $700.00 scanner. So, with that being said I am completely baffled with this one to the point I’ve taken insurance down to collision and stopped attempting to drive it. Oh, never been wrecked or flood any of that so I have all the proper troubleshooting tools just need some help of where to start this process and please whoever helps me don’t give up. I’ve seen many have this problem and it never be solved I’ve got 20+ years GM experience, let's do this!