Southern had a handful of GP39Xs, which were basically pre-production versions of the GP49, and are externally similar.  Prototype photos can be found here, and excellent information can be found in Hundman's GP49 book (the same people who produce N-Scale magazine).

 

To recreate this model, I will start with the chassis, sill, cab, and trucks (with "snubbers") from an Atlas GP40-2.  The short hood will be pretty straight forward, but the long hood is going to be more involved.  The intake and dynamic brake sections are shifted rearward some three feet, as with the Phase III GP39-2s and GP49s.  The radiator fans are the type found in GP50s and SD50s.  And the radiator grilles are the larger types also found on GP50s and SD50s.

 

So this project will get pretty involved, and I won't be tackling it until after I get some other projects under my belt.

 

UPDATE: 6/16/06.  The same source that produces the GP38-2 long hoods that fit on Atlas engines should also be capable of producing long hoods for the GP39X.  This project will be the next one to be performed after I can attain one of these hoods.