Wait, are you asking 40k to Inquisitor, or Inquisitor to 40k? You said both in your post. I'm assuming you mean Inquisitor to 40k, though. Its kind of hard to do this, because Inquisitor is much more fluffy rules-wise than 40k, with Space Marines with extremely high toughness and strength and such. I would say that normal stats for that race + a few wounds would be good for powerful characters (for example a 3-wound Inquisitor would make sense, but not a 3-wound Imperial Guard veteran) and then *most* of the equipment is easy to convert into 40k, and you can even look at some second edition rules if you have access to them, since some things in the =I= book were also in second edition. Of course some rules would be unbalancing in 40k (for example, every weapon causing pinning tests), and some could not even be implemented without a giant paragraph describing what it does.
