Chevy Caprice wont stay started and its overheating

I'm having problemswith my 95 caprice, I bought a brand new battery, optispark distributor, coil pack, plugs wires, throttle sensor, all new and I'm still having problems. The car will turn over and start for about 5-10 min, then it will overheat and shut off. It's also not idling rite and acts like it's doesn't want to idle at all. It also will mainly only stay started when I have my foot on the gas, when I take it off the car shuts dow me personally I think the harmonic balancer may be off but I'm not a mechanic. Any tips or information would be greatly appreciated thank you.