Open element drop base air cleaner wo vent tube
 

Anybody happen to know the original application for a drop base without the punch out for the passenger valve cover vent? Looks like a 1967 L88 but are there others? I've had this thing for so long I can't remember where it came from.

Thinking further on this it may be a parts counter piece. i wonder what the part number would be. Definitely GM though.