Manifold casting/PN ID help needed

After having the hope of using Magnum exhaust manifolds on the Demon dashed due to insistence on having power steering, I'm looking to open things up with conventional manifolds. I found a pair that are supposedly off of a 360. I'd like to know what I found in my own junk before I go off in search of something else. I don't know if these are part numbers or casting numbers. Please set me straight as to what engine/body/year combination in which these were used. Thanks.

LH 2780945

RH 4083826

The right hand manifold was very hard to read, so the number is somewhat suspect. It did have J168 on the left hand side. The exit on this manifold faces down in the center and has ribs cast into the 4-6 runner.