Dave,
I tried to subtly correct your F55X in a post above.
Just so people know (and, correct me if I am wrong) F255X is an indicator that the Flint-build ("F" prefix) truck 235 (designated but the "X" suffix) is a 2nd series truck (designated by the preface "2").
255 was not used for any 1955 car engine (right?).
Did all 1955 car engines use the low-mounted ("internal") water pump as was only used on "255" and later truck engines?
And, finally, 255 used on any 1955 Jobmaster 261 truck engines?
