The intake would be correct for a CNR 350 300HP engine from a B-Body.
3965577 1970, 350, 4bbl iron Qjet, B F X, 300HP or 350HP.
A280 = January 28, 1970.
3970010 = 1969-1980, 350, 2 bolt or 4 bolt. The higher output CNR stamping probably means it's a 4 bolt main but you won't really know til...