Manifold/Header/Pipe questions

[Rickracer]

I've been told that a Zen W/C manifold and/or won't fit the Homie motor. Why is that? Different bolt spacing? Different pipe size? Right now I'm running a steel manifold/header I whipped up at the shop along with the chamber from my K&B 11cc, but it's melting the silicone connector, and I really like the idea of water cooling the manifold. I'm betting the chamber is probably too restrictive and/or not the right sizing for the Homie, but it seems to be faster than the gutted and Zoomied stocker muffler. I'd like to get a manifold/header that would work on the Homie and a Zen or Sikk motor to give me some flexibility in the rigging of my "fleet".