Just to make sure I am understanding this, the port and sbd manifolds are not the same, and when mounted on the engine the main exhaust ports are slightly staggered?

I can't find anything that says there is a diff. in left and right, each manifold should have plugs on both sides of the riser for water feed, as far as installing to the block there is no diff. in left and right, and the risers should be centered on the manifold.

There is no difference on the Stainless Marine manifolds and risers that I installed in Feb. on my small block, only thing I had to do was cut 1" off the corsa divertor on the port side account the riser is a little longer than stock starboard side was fine hope this helps Steve