I had the same problem in my 79 with a 400. My problem was that when I'd stop my truck I couldnt start it untill it cooled. One of those times I happen to have some water and I poured it on the ignition control box b/c It nearly burnt my hand when I touched it. After I cooled it off the truck fired right up. I bought on from AutoZone but eventually ran into the same problem...I bought my next one from Checker an its working great....I kept the old one as a spare...The symptom for my truck was that when I tried to start nothing would happen...

Hopefully this helps...

John