The new SCS&W IV says, discussing the Model 24-3 and later guns, that 5 and 5-1/2 inch are rare. I think that is wording that was just carried over from the discussion of the earlier 1950 Target / Model 24 in previous editions of the SCS&W. There were 5 inch 1950 Targets made, mine was shipped in 1952. Also, in discussing the variations produced of the 24-3 and later guns and their product codes, no 5 inchers are mentioned. I have asked on the S&W Collectors Association side of this site if anybody has ever seen a 5-1/2 incher, but nobody had.
A couple of folks on this site have had their 24-3's bobbed to 5 inches and, like the Models 27 and 29, they make great holster guns.