Lionel did make the 3751-class ATSF 4-8-4, but not the 2900. The 3751's are similar to the 2900's, of course, but are an older, smaller class and not quite as massive.
I'm wondering if Lionel bought the MTH tooling for the 2900's and we may be seeing that loco in Legacy one day. They just released the former-MTH Santa Fe 2-10-4, and I believe that the boilers are the same piece for both locos (the real locos had a similar relationship).
I'd go ahead and convert the PS-1 version to ERR; much cheaper, simpler, and runs really well.
In an interview about the current catalog Ryan mentioned Lionel bought the MTH tooling for both the 5011 class 2-10-4 and the 2900 class 4-8-4. They decided to run the 5011 class first because they just ran the 3751 class two years ago, and Lionel figured the 2900 class was too close for most people to differentiate.
OP I have two Premier 2900 class 4-8-4s, 2903 and 2921. I run TMCC/Legacy and DCS, so I installed PS3 in both of them. They should take ERR no problem. The one below is a factory PS3 version that I got unpainted and was missing all the wiring, electronics, drive line, and motor, so I painted and put it together.
This was a PS1 version I updated to PS3 and detailed. I blackened all the shiny trim and wheel rims, added bell cords and guides, painted the smokebox graphite, and added a movable stack extension.