Crossram Expert Needed

[musclecar fan]

I just purchased a portion of a large NOS and rare parts collection from an individual that focused on the rarest of the rare. One of the items he had for over 40 years was a fiberglass air cleaner base and it is in a box with GM labels, but no part numbers. I'm not sure if it is a prototype, SCCA or CanAm piece, aftermarket or what, but I remember talking to him 35 years ago and he said it was a super rare item. Can any of you shed light on this or direct me to a crossram expert who might know? Thanks