High five! Beat me to that reply.This confuses a great deal of people.
The SD70M and SD70MAC from their early 90s introduction to the early 2000s had flat radiators, like 4569 and 4674. These are SD70Ms; UP has no SD70MACs. Then they got slightly flared radiators, like 4841. UP has many flared SD70Ms; flared SD70MACs are much less common, only found on CSX and Alaska Railroad. For the past few years, they have been replaced by the SD70M-2 and SD70ACe. Despite the mismatched designations, these are the DC and AC versions of the same engine. They look somewhat like SD90s on SD70 frames. UP has SD70ACes, and none of the less common SD70M-2.
Deano, & all, modelrailroadtips.com has a simple number by number list of the SD70M's on UP, with the body style, and some paint hints:
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