According to STASH, the motive power on the Tidewater Southern was 70-tonner # 743.
I was able to cull more of his story from another Board, to wit:

"The excursion began at the Western Pacific station on Third Street in Oakland
and ran over Altamont Pass to Ortega. From that point we
were on the TS and stopped for lunch and a tour at the Franzia Winery before
continuing to Turlock and returning to Oakland.

It was too long ago for my recollection of a stop on Ninth Street in Modesto. I
do recall waiting for clearance at the SP interlocking.
Power on the WP were F units to my foggy recollection. The passenger count was
heavy and the long train turned more than a few heads
along the Tidewater Southern that day. I don't recall the name of the special,
but believe it was a BAERA sponsored train. I have more
photos but they're mostly of the various cars on the train. Included in the
consist: Circumnavigator's Club, a Santa Fe heavyweight
Snack Car, UP heavyweight observation 1536, NWP coach 458, WP 653 -- all vintage
stuff owned by clubs and used on excursions of the
era. Fun times."

---stash