5KS Intermittantly stops while driving

[Murray440L at aol.com]

I could really appreciate some help on this one.  The 1987 5000s
intermittantly stops running.  I at first thought it was the fuel pump, so I
changed it.  No Luck.  It stops sometimes while at idle, sometimes on the
highway, no particular pattern, sometimes cold sometimes hot.  The fuel pump
I can still hear when this happens, but all the lights come on the dash and
it's dangerous because it's not easy to brake  to a stop if you're not
prepared for not having any power to go with them. I assume it's something
electric, either a ground, relay, or something in the ignition system, but
have no idea where to start looking.  Please help.  Mike