Looking for help to indentify EMD Bachman Locomotive

[wrestling #1]

I recently purchased a Bachman Military camoflouged locomotive #4098 on ebay (item #120337162946).  It looks exactly like my EMD SD40 in design, except that it is 1 1/4 inch shorter in length, only has 4 fans on top, and only has 4 drive axles instead of 6.  All other features look to be the same except for the design of the fan grills and upper ventilation panels (same location different grills)  The difference in overall length is due to the shorter length design of both the front and rear porch.

Can anyone tell me what model of Bachman this is, as I would like to upgrade this to DCC?  And because of the tight interior design, it looks like I will be forced to exchange the shell to a new DCC unit, rather then adding a dcc decoder. 

Any other information would also be nice to know about this unit.
Thank you for your assistance!
   

[the Bach-man]

Dear Wrestling,
It's a GP-40. Your easiest course of action is to get a new DCC Onboard loco and switch shells.
Have fun!
the Bach-man

[hindmarch]

Hi WrestlingI,I have the Bachmann US Army camaflaged set which was dc ,i installed a Digitrax Decoder in the loco without too much trouble,You may have to cut a little from the weight but that is not a big problem, This was a "N" decoder and it runs without problems, i dont see why you have to spend $ when its not neccessary.Bryan

[gregohio]

MB Klein has the DCC GP40's for $30.  Pretty close to the cost of a decoder alone.

[wrestling #1]

Thank you everyone.

Question: 
Are these shells interchangeable between different brands? 
Or should I stay with a Bachman loco to insure that the shell fits correctly? 

[Conrail Quality]

You should stick with using a Bachmann mechanism. Different brands use different methods to attach the shells to the mechs, so, for example, an Athearn shell might not fit onto a Kato mechanism, even if they are models of the same prototype.

Timothy