UP is freeing up the 8000 range for a new order of GE's. The batch that is being renumbered are the ones that were delivered in the 8000-8308 range with a 4300 HP 710 engines and meant to be "upgraded" later when the higher horsepower power plant became available. UP never did, so in effect, they sort of are SD70M's. UP has already retired all of the "true" 90M's in the 8500-8561 range that were delivered with the 6,000 HP "H" engines.
Hey thank you for this information. I'm not surprised they scrapped the 6000HP because it was a beast to get a train going. EMD tried to put GE in a huge engine not designed for what was expected of it. Only CSX and CP bought into it.
I'm sure I will see one of these renumbered 9043ACs come through here. I know I've seen some in the 8000-8308 range. I think I have some of them documented in my locomotive archive on here.