ignition issues 78 impala

My daughters boyfriend hooked up jumper cables wrong and tried to start the car. It burned 2 wires to the starter and the starter. I replaced starter, alternator and ignition switch. The car will start but it wont stay running. There is no power in the run position to anything but when i turn all the way to start it starts but stops as soon as i let go of the switch. I tested power and i have power to my ignition circuit when its in start position but not in the run position. Any help would be appreciated im at a dead end. I have a manual for it but it just gives you the basic ignition circuit and not a detail of the what holds the run position.

Sounds to me the ignition switch itself was fried. However there are fusible links along the main harness. I had an issue a few years ago on my 79, got no power to anything. I completely rewired it and removed all the fusible link, and installed a 250 amp mega fuse right off the battery. I have the full wiring diagram for these cars, they're posted on here too.

I think im misreading your post. You checked power right at the pink plug on the distributor? If so thats directly from the ignition switch, meaning the switch is bad if your only getting power in start position.

I replaced the ignition switch already. Yes i only get power when the switch is in the start position.