Anyone who buys the B&O version of the 2-8-2 will need to swap the SP Vanderbilt that MRC is leaving on it for the B-mann USRA standard, anyhow. I am aware of only one Q-3 that had a Vanderbilt. It came from a scrapped EL-5. It was swapped in near the end of the steam era as B&O, as were most other roads, was dismantilng steam facilities.
I am suprised the MRC did not make the relatively simple correction on the tender. When MP was producing its small steam engines, it announced the SP version of its eight wheeler with that same SP Vanderbilt. When the SP modellers sent MP e-Mails, they caused Ajin, or whoever, to make a box oil tender for it. If MP could make a change, why could not MRC?
Most of SP's E-classes did have a box oil tender, but there were a few that had Vanderbilts,. In fact, the old MP Vanderbilt is one that SP did use on its smaller steam power. Harre DeMoro's book on SF Bay Area steam has a photograph of an E-cless with a Vanderbilt.
Southern Railway did have a class of Pacifics that looked much like the USRA heavy rather than the USRA light. If there was a Southern Railway pacific that looked anything like a USRA light, I have never seen a photograph of one.