I'd sh*t a chicken if the rotor pack fit. It's gotta be longer and/or fatter. Isn't the BCM a tiny plastic box? Can you just force feed it a power or ground to make it happy? On my trucks and the Corvette, the passlock module gives the PCM a handshake when everything checks out. Easiest way around that is to tell the PCM not to care.
M90, 112 and 122 have the same diameter pack family. The lengths are different. It's generally 15 cubic inch per inch, so a m90 (90 cubic inch per rev) is 6" in length, a 112 is 7.47" and a 122 is 8.125. M62 and smaller (think Cobalt SS, early Bonne SSEI) are a smaller rotor diameter.
It's not rare for people to make a spacer plate and stick a m112 pack into a m90 housing, the problem is that a m112 and m122 are gen 5 packs and my m90 is a gen 3 pack, a gen 5 pack mounting flange is significantly different than a gen 3 pack.
Basically a 112 pack in a 90 housing needs a 1.47" spacer and a slot cut in the lower intake. The M112 lightning blower sitting on my workbench has a 1.5" shorter snout, so if you buy a lightning m112 and an adapter plate and a have a gen 5 blower the belt drive basically sits right where it needs.
If I had a 04+ GTP blower instead of my 97-03 I'd very much consider a pack swap. The bolt pattern on the snout on how it mounts on the housing on gen 5 is different than gen 3 also, so to run an extended gen 5 pack you need a gen 5 housing.
Long story short, this case swap will work for my fiero buddy who wants me to machine him the plate, who has a gen 5 blower, but as I have the time invested in this gen 3 blower i'm kinda stuck there. If I went M112 pack swap I'd need to re-weld an elbow onto a new M90 housing, get a gen 5 lower intake, which is more than I want to deal with to make the car run another second faster in the 1/4 when I already have a car that runs 11's.