CC,
I've got a couple M90's off GM 3.8 V6's. They are pretty long for a longitudinal engine. A shorter snout can be had, but the throttle body is mounted on the back of the blower. Getting one into most engine compartments can be a hassle. Transverse, not so much of a problem.
The Ford Thunderbird version mounts the throttle body to the side instead of axially in reference to the rotors. That version is much shorter.
One I have is a good take off, the other is a fresh rebuilt from Holley. Folks hear a rattle, and they replace the blower for a bucket of money. The problem, generally, is a ten dollar coupler.
M90's or any of the Eaton's are Blowers, not compressors. At low throttle settings, they have a bypass that allows the blower to idle, without a lot of power loss. When you put your foot in it, the bypass shuts, and you start stacking air. Typically, they don't make a ton of boost. I don't know how much you can get out of one, but single digit boost numbers are typical.
The Eaton has a self clearancing coating, which does not tolerate fuel. They are designed to run dry, not in A/F mixture. Some folks remove the coating with oven cleaner, and run them that way as a draw through. Though not as efficient, they still build some boost.
CJ
