Severe Miss

Probably just badly in need of ignition timing adjustment -- it will have changed dramatically in replacement of a slack timing chain with a taut one. I had exactly the same situation the first time I did a T-chain-and-sprocket swap; the timing had shifted so far off that the sparks were jumping randomly to the wrong cap towers because the rotor was closer to the wrong tower than to the right one. And that was with a 6-cylinder with relatively wide spaces between adjacent cap towers; on a V8 this space is narrower so it takes less of a timing shift to cause the problem.