As far as certain assembly plants using Eldebrocks, it wouldn't matter. Aren't motors are assembled elsewhere? I have heard the pin hole problem theory before, also two other speculations, surplus intakes being used up and low supply of iron intakes (there were a lot of Six Pack motors being built in Aug-Nov '69). I don't think the issue is if they were used, it's how to prove which cars got them. This of course is most likely impossible.
