Question for nailhead experts. I've got a customer whose got a later nailhead engine in his Skylark. He claims that others say it is NOT a nailhead. It does have valve covers that are straight up, and a distributor in the front, which is supposed to be the defining point that it is NOT! So is it? Or no? If not, what are the major differences? Can he use a regular nailhead 4 bbl intake? He tried getting a Pertronix for it, but it didn't fit, and Pertronix said it doesn't have an application for this particular engine. Sounds like it's an oddball intermediate engine, that doesn't belong to any family.