These animated GIF's illustrate the difference between original drawings (done in 2000-2003) and revised versions (first started in April 2005).
EMD Locomotives
EMD
GP40-2W
EMD
GP60 (Demonstrator)
EMD
SD40-2, Phase 1
EMD
SD45, Phase 1a
EMD
SD70M (SD70I substituted for original drawing)
GE Locomotives
GE
B23-7
GE
C39-8
Michael Eby 2007