The timing chain was what came to mind first for me too. Has your engine ever been rebuilt? If not, it may have one of those nylon toothed cam gears. If that's the case I doubt there is much left of it and the chain might have even jumped a tooth or two.
While you have your distributor cap off when setting the #1 to TDC you can check for slop on the timing chain. Turn the crankshaft one direction until you see the distributor rotor move. Now turn the crank the opposite direction until you see the rotor move. How far did the crank move before the rotor moved? It should be nearly instant to just a couple degrees. Any significant movement before the rotor moves will indicate a loose timing chain.
Another thing that can cause these symptoms is a bad camshaft. You may have one or more flat lobes. While you are tuning your engine over by hand to set TDC and checking the timing chain, remove the valve covers so you can observe the rocker arm movement. All rockers should move about the same amount. If any don't seem to move as much as the others it is an indication of a worn cam lobe. You can measure this with a dial indicator but a significantly worn lobe will show up as a rocker arm that is barely moving. Real easy to see without any special tools.
Continue turning the engine until both valves on the drivers side front cylinder (#1) are closed and stop with the timing mark on "0" to be on TDC.
Tom
