Do we have an very good line drawing or very good side view of that AN/SPG-55. Because I have a felling that there is something wrong with the drawing... but that perhaps me!
Looking at this Leahy picture, there do seem to be substantial differences. I have to back Heuhen here. Having already found some sources, I'm willing to give it a shot. Might take a while though.
Edit: Nice picture of the SPG-55 aboard Belknap, a month before her collission and subsequent fire. Taken from the Krasny Krim, a Soviet destroyer. Seems to be missing the crossed strengtening bracings present on some other sets.