The port openings of the 292 are the same as the 250 since they both use the same head, so from port opening to exhaust exiting the manifold would be the only change area. I would bet side by side, the manifolds are the same except the outlet diameter. I am sure there was reason for the larger pipe diameter, but for everyday driving, I real doubt you would see any difference.
It would be a good test for someone to try.
