[iluv69s]

First of all, the repo tops fit the GM bottoms. Second, the early prototype intakes all bolt up with the later tops and bottoms. The changes were minor once they started the 'production' intakes.

The bottom does not look GM to me off the top of my head. I see no bosses for the oil sheild mounting points that the early units had. These bosses were on all the intakes even though they cancelled the oil sheild. The top looks like a repo also. It is difficult from pics because the repos are pretty good. If you can post some closeups of the edges of the intake top and also the mating surface where the top mates to the bottom, I can tell you definitively. The machining marks are a giveaway between the new repros and the originals.
I can pull out one of my original intakes to compare. I also have an offy intake that ill look at to compare. I would bet that you have an Offy base..and a repo top.