Manifold swaps are probably the most common modification out there, best that number will get you is an ID on the intake itself.

There should be a small pad on the block, right under the front of drivers side head (I think drivers side). Take a wire brush to that area and see if you can't make out the stamped block number there. Also may be cast into the driver-side side of the block above the freeze plugs.

Pretty sure on the locations, others will probably confirm. Its been a decade since I looked, so go easy on me guys.