Rick,
No problem. The info I posted is from pretty much from John. He doesn't frequent this board, so I had asked him to post cause he always has more details.
Here's a quote from him that clarifies the mask used:
"Both plants used a vacuum-formed plastic mask on aluminum intakes during painting..... Engines that also had aluminum or chrome valve covers used a similar mask that had "wings" on it that also masked the valve covers."