D&H GP39-2 7410, acquired from RDG at Conrail startup. Some ex-RDG and Lehigh Valley locos eventually got a coat of blue, but some had needed a better wash and the previous colours came thru. Quite a challenge, almost an oxymoron - fantastic weathering. In O-scale, start with a Weaver GP38-2. I think the local US toolmakers (not China) may have worked to data taken from a Lehigh Valley GP38AC that was parked nearby, hence the wider spaced fans at the end of the long hood - right for an early GP39-2 - and leaf spring Blombergs.
So on the Wvr GP38-2, take off the air filter (square cross-section box) ahead of the dynamic brake which has to be lengthened to fill in the space to the blower grill. Yes there are other smaller differences (exhausts, etc). If you update all the fan section (see the blank bit bfore the d/b wide bit starts) with Des Plaines fans and grills, you can end up with a 3xfan GP-40-2. Don't forget the trademark RDG rainwater deflector on the cab roof. I have one nicely converted by Chris Iverson, yes I should take its pic, incidentally are you out there Chris?
Jason