1985 Chevy Caprice Extremely poor runability issue

You can get this car to run pretty good setting still. When you put it in gear and go to drive it, it coughs chocks gages and pukes like you never seen before. We put plugs and wires on it already, put a pick-up in the distributor. Put on a new coil, tried to check for vacuum leaks. Engine will rack up fine most of the time in park, seems to be getting plenty of fuel, has new cap and rotor, new fuel filter, we even got it up to speed once on the interstate with plenty of fresh fuel and water remover. We bought this with the problem, figured it would be an easy fix. I still think it will be if we knew what was wrong. We are stumped. Help please ! We think mileage around 85000, but who knows for sure. Looks like they have done head work on left bank.