Help with Atlas GP 38 duel mode decoder

[randyaj]

I purchased two Atlas GP 38s with the duel mode decoder decorated in BN. I have recently decided to backdate to the late 1950's. I listed the engines on ebay for sale but did not recieve the minimum price that I set of 75.00 (I paid over 100.00 and ran them once). They are such beautiful running engines that I don't want to sell them for less. And so I come to my question. Is there anyway that I can by changing cabs or limited kitbashing backdate them as well? I am willing to repaint them but don't want to do a major rebuild. Any help out there?
Randy Johnson
Iowa