Someone gave me an Offenhauser 3x2 intake manifold but he doesn't know what engine it's for. The only numbers are on the underside of the intake. The number 3558 appears and I assume it's the part number. Also appearing is the date--3/3/81. I have a feeling it's used on a GM product since the distributor hole is located at the rear. Anybody have any idea what it could be?