I have used the upper con arm access holes for fresh air before, although not on a 6bbl. On a couple of different 4bbl cars, I used an older GM diesel truck air cleaner assembly, grafted on a drop base and grafted on a pair of the cold air ports from a Diplomat and used the hoses from the Diplomat to the access holes. Almost everything came from the pick-a-part yards.

It wasn't pretty, but was totally functional. But your 6bbl set-up will make it a lot more difficult to seal the carbs, I think.