have thought about this as well, and have an eaton m62 supercharger from a gm 3800. think it's a genII, but not certain on it.
the m90 eaton is a little larger, has a longer snout, and may fit a little easier to route a belt to drive it.
regardless, the m90 was also utilizedon the ford 3.8 in their supercharged t-birds and cougars. it's more 'boxy' than the gm versions, but doesn't have a bypass valve in it, iirc.
either way, all of these units will not fit under the hood in the location that you indicated. a custom lower manifold will need to be made.
i am in the design stages right now, and plan on running a meth injection system as well.
here's a few teaser pics....
you can see the bypass valve in the last pic.
df