I emailed the photo to a knowlegable passenger car guy, who replied:
"The second car is some sort of heavyweight. You are seeing the air conditioning ductwork on the roof along the clerestory." It still looks like a dome to me.
Also if this is an Aug. 1986 photo, then it may be CSX. At least I've read where the CSXT was formed from the SBD in June, 1986. From Wikipedia:
"Once the ICC approved of the merger, the Seaboard System Railroad was renamed as CSX Transportation on June 1, 1986. The railroad began applying the CSX Transportation logo and paint scheme on a few of its locomotives. On April 30, 1987, the Baltimore & Ohio was merged into the Chesapeake & Ohio; with the C&O merging into CSX Transportation on August 30, 1987. All the major parts of CSX were now one company."
or
"Effective July 1, 1986, the Seaboard System was merged with the Chessie System to form CSX Transportation."
Stew