Will not stay running?

I have the truck listed above, it had a 5.2 swapped it out for a 59 and it ran fine. one day going down the road it just shut off of the blue. The kids lost the key to it. They drilled the ignition, and they found the key to it, but the truck now that we've got the transmission issue fixed. It was the flesh plate that had broken. We fixed the flex plate now the truck just starts and shuts off. I got fuel pressure at the rail and spark and if you spray starting fluid in it it'll run just fine until you stop spraying and then it shuts off. You can hear the pump come on when you turn the key to the on position when you go to start it, it just fires up and then shuts off, fires up and then shuts off. Please help. replaced the crank position sensor, but like I said it fires up and just shuts off. I think it's got something to do with the ignition that they drilled out, I already read somewhere about it it's got a oh I can't remember the name of it I think it's a scam skim system, but would that cause it to start and shut off. the truck was running fine before the flex plate broke replace. now I got this problem. oh yeah, I forgot when it before they drilled the ignition it was we were using the key but it's not a transponder key it's just a straight Metal Key and it was running fine working fine. so, it's not a transponder key that that is the issue. I don't think I'm not really sure need some help it was sentry Security System.