Sorry to beat a dead horse but I'm looking to upgrade a 455 in a 68 442 to HEI. Trying to repair the hack-job the previous owner did (now the engine won't continue to run due to a "homemade" harness"). What all do I need to do a full conversion from scratch?

 

I dont know whats been done to it, but all you need to do it put in the HEI, and run a primary wire from it to someplace convienent.

 

So I need an HEI Distributor?

 

I think your best bet would be to get yourself a good wiring diagram. I remember from your other post that you are searching and asking about the manuals that are on cd. If you consider buying one of those it might be a good idea to print the diagram and if you have a good machine, you could enlarge it to a good legible size, then paste/tape it to a corrogated paper backing to keep it rigid and prevent it from blowing away while you use it in the garage or wherever. Even if the diagram is not in color it would have to label the colors of the wires or else the diagram is useless. I did this once and it worked well for me. Perhaps a little research at the library on the automotive ignition system (in general) would help you out to better understand where you need to get to starting from the place you are now with the original wiring gone or changed so much. I hope this helps out and good luck in your efforts.
I guess I may have missed your real question about HEI. Why do yo want HEI in the first place? IF just for dependability and ease of maintenance compared to points ignition, consider an upgrade like Pertronix provides. That way you could concentrate on correcting the the wiring to original condition by following a diagram and then make the required changes for the Pertronix kit (which is very little).