Old memories from an older brain...
Smithsonian History and Technology (the one with the Southern 4-6-2) USED (1970s) to have an EMC diesel engine on display in their railroad hall-- I ***think*** it may have been from the original [email protected]
"Zephyr," in which case it was a 201A, though a smaller one (straight 8 ?? instead of V-12) than the ones in the ATSH and other early 1800hp passenger units.
Original "Pioneer Zephyr" is preserved-- USED to be a Museum of Science and Industry, Chicago but I think has been moved. A "sister" train (for B&M?) has also been preserved. Don't know if either has original engine.
I think B&O museum, Baltimore, has some early EMC 1800hp passenger unit, but don't know if it has engines in it, ore (for that matter) whether it was re-engined before retirement.
Sorry not to be more helpful: at least I've lengthened the thread, and if it LOOKS active maybe someone who KNOWS the answer to your question will post!