Hey all -
Just had the truck running yesterday after replacing the battery from 2018.
It definitely needed replacing. Once I got the new battery in, it started up instantly, and I drove it around for about 20 minutes or so before parking it in the garage.
I did notice that the ALT light was on, however.
I went to drive it today locally to get it registered in state - was able to start it up on the second try, however once I put it into R, it just died out.
Did this a few times with the same result.

So with a new battery - I'm guessing it has something to do with the alternator and a wire perhaps?
Quite new here so any help is appreciated.

 

this is for a 1972 F-100 Custom.

 

Do you have anything more to report on your Alternator Light and stalling problem?? Cap

 

I would start by putting a volt meter on the battery with it running, if alternator is charging it should read 13.8-14.2 volts. Is the alternator belt tight and not slipping on the pulley? Not quite sure why it dies out , if the battery has enough juice to restart the engine it should be enough to keep it running, even if the alternator isn’t charging. May want to look at a loose ignition wire or coil wire. Some times the small lead from the coil to distributor will get a bad spot and ground out
Good luck