I got the cab/hood home last week. When I bid I thought it was a M915a2 cab, it turned out to be a M915a3.
The differences:
A2 uses tachograph (of which I have a brand new one-I liked that about it because it was easily adaptable to the NTC400)
A3 has a separate tach/speedo, this will be fine but I may have to find the transducers to make them work.
A3 has heated mirrors, haha!
A3 has Eaton Vorad radar system, I am removing it and selling it (I don't have the radar sensors and they are very expensive)
A3 appears to have power mirrors (switch for each side goes up/down but just says 'mirror power')
I have already removed the Allison Transmission pushbutton shifter, wiring, and computer (oh how I wish I had an Allison to put in it!).
The Vorad system is out, but still has some wiring I have not gotten out yet.
The differences I can see for mounting:
Rear cab mounts should be easy enough to adapt, the bolt spacing is wider than that of the AM General.
Front cab mounts are completely different, they are further forward and just above the frame, as opposed to further back and outside the frame.
The big firewall mounted oil cooler will need to be mounted somehow, as will the air cleaner, they will likely need to have brackets built to bolt them to the frame, as there is not much room to bolt to the cab firewall.
The cab is MUCH more roomy/comfortable than the old cab, even with air ride seats in the old cab. The tilt/telescope steering wheel is nice too.