One thing I must say is SHS rail was NEVER advertised as code 125. That was spec and fud. It was advertised as 155# Pennsy rail, and it is.
Pennsy and SP did some 6.5" rail that was tall and thin. Most 155# rail was is only 6" tall so it is code 125. The 6.5" rail is taller. See the confusion?
SHS and now MTH rail is spossed to be code 131 -0 +6, most is closer to code 133 or 137.