T.Mott,
See no need to worry about HEI. Get one out of Caddy in the local junkyard, drop it in and live happy with it. I used it in a bunch of cars, both of mine and from some fellows, and all I can say is that it is just the more reliable sotck ignition system I've ever used. Just get one for the intended use and no problem.
But to be honest with You, I'm not sure about blaming your ignition system for the misfire. Some other problems may be going on. Are You definetively sure there is nothing else wring with it? Just imagine if it's not the lifters i.ex, weak valve springs, You say the engine runs smooth cold, then gets hot and starts misfiring. Is carb problems totally out of question? Guess it's a q-jet, huh?
