The GM part number for the air cleaner assembly is 6484584 (69 Camaro & Chevy II w/350 4BC w/A.T.) as per my 1969 Corvair-Chevy II-Chevelle-Camaro Parts Catalog (Oct. 1968). The M.T. air cleaner is part number 6484583 for the same model. If you find one at a swap meet there should be a white sticker on the side of the base with the part number but most of the time this sticker is long gone. I have 3 original 1970 Camaro SS350 air cleaner assemblies (GM # 6485242) as well as an original 6485240 air cleaner (1970 Chevelle w/350 4BC), all have the white stickers with the part number.
Good luck searching.