NW2 diesels

I have done a few comparisons earlier in the same vein.  The shell (I was using a 614 shell on a 6250 frame)  will fit, but the mounts are different and will require improvising.

The Blomberg (GP7 as you call it) are staked on and the AAR A (alco type as you call it) are screw on, , there MAY be a Blomberg from an F3 that would work (with modifications).  The GP7, later NW2s, "44" tonners mount with speed clips on tongs, the early NW2s sandwich the frame with the motor and truck - totally different.

Question?  Why put Blomberg trucks under and NW2, they never had them and Lionel was incorrect (as in many other items, they made nice toys for the most part).  NW2s might have had Flexicoil trucks, I've never seen a picture though, but not Blombergs.

It would be very rare to find a real NW2 with Blomberg trucks.     I think first off they probably are too long in real life.    The AAR truck used on most switchers up to the last few models was a shorter wheelbase than the ones on Alco road engines or others such as GE U25s.   

The loco in the photo you posted is not an NW2.    It is one of the last of the SW series or perhaps the one they named the MP15?    I don't know the models of these.  

You can use sideframes from 2333/43/53 (silver), 2344/ 2354 (gray) and 2356 for black for screw on replacements for the Alco sideframes. A block of plastic will need to be JB Welded to the geared side of the sideframe to keep the gears from falling off. I think Rock Island had a couple of SW's with road switcher Blomburg trucks.