The two-barrel intake and carburetor would be stock items on the GMC 302. The dual exhaust is more likely to be a modification. Does the "forward" outlet appear to be cast as part of the manifold, or is it welded onto the manifold? If it is welded, then you have a "split manifold."
The oil filter would be optional equipment in the 1950s. You can modify the block to use a modern, "full-flow" filter.
God's Peace to you.
d
Inliner #1450
