sorry for late reply but I only just stumbled onto your post.
Data sheet brings this engine up as originally a Big Cam 290, CPL-353. If there's no after cooler fitted then its probably still a 290..
Built on April 19th 1979 it went into service and warranty started on July 31st 1979.
Looks like its a Big Cam 1 with 60lb oil pump and large oil cooler.