Paul, I have a #3917610 on my car, and I have seen #3890490 (L79) Intakes are both Winters Foundry. There are other differences, in other areas both are very similar in this area. I am wondering with the quality and size of these pics. how you can be so sure? I'm not saying your wrong, just wondering. I don't see anything that definite.
Mike, I have the above (and now below) pictured manifold in my garage. I pulled this one off a wrecking yard '68 Z/28 back in 1982, I just didn't know why someone changed the oil fill tube.
P.S. I apologize for the lousy iPhone photo.