Three of my upgrades have been posted (more to come). I'm just a runner who hates shelf queens.
Upgrades/conversions posted so far are MTH 20-2151-1 (1998) AT&SF F3 AA Set with added 20-2151-4 powered B unit (4 motors), MTH 20-3021-1 (1997) UP Big Boy, and MTH 20-3025-1 (1998) SP AC-6 Cab Forward.
After I finished with the Cab Forward I realized it would have been interesting to investigate the possibility of placing the PS2 board in the boiler instead of the tender.
See Upgrade listings and links here http://www.slsprr.net/technical/mthps2upgrades.htm .