Ground circuit on 1995 GMC 1500 Sierra

I have problem with 4.3 engine running after it starts up and runs for about half hour, I believe there is abreak somewhere in the ground circuit I added a new ground strap from battery to block where else should I try adding new ground circuit because I feel when driving ignition seems to cut out, then when you let it sit for afew minites it restarts till problem happens all over again