Truck dies and has no power?

I have a 1978 F150 with a 429 big block. I was driving and everything started to get dimmer and dimmer. It started to sputter and then died. i popped the hood and seen that the alternator ground was off and sparking, so i connected that back up. hooked up a pair of jumper cables and tried to start it. nothing had any power still. wouldnt even crank over. I have no idea what it could be so any help would be great. thanks.