car trouble

I replaced my alternator and battery on my
83 El Camino because it would crank one
morning without a jump off apparently that
wasn't the issue if its parked running the
engine sounds fine but it I go to the tail pipe
it sounds rough I drove it everytime I give it
gas seems like it wants to shut off when I
park and and try to crank it back up it does
nothing not even turn over have to jump it
back off to crank it and with the lights on the
motor gets low can someone give me some
advice.