At this point I'm not going for perfectly authentic, just close enough, as I'm starting with an imperfect model and modifying it. After all it's going to run on 3 rail track, so there will be some compromises. The plan right now is to use a Williams USRA Mikado as a base with the above Vanderbilt tender, so I'm going for scaleish size and close enough, because this is going to be a fun project for me. I plan on adding the following parts to the Williams USRA Mikado to make it close to the SP prototype:
http://stevensonpreservationli...5&products_id=47
http://stevensonpreservationli...&products_id=223
http://stevensonpreservationli...&products_id=231
http://stevensonpreservationli....php?products_id=263
http://stevensonpreservationli...&products_id=252
http://stevensonpreservationli....php?products_id=240
http://stevensonpreservationli...&products_id=293
http://stevensonpreservationli...&products_id=334
http://stevensonpreservationli...9&products_id=76
http://stevensonpreservationli...&products_id=327
The above items should get me "close enough" for 3 rail Hi-Rail.