Matt is correct, but there are a couple other items between ATLANTA and JUNEAU. Both were built by Federal SB, Kearny, NY. SAN DIEGO and SAN JUAN were built by Beth-Quincy SB, MA. The bridges on the Federal and Beth-Quincy built units were different. In both cases the first unit completed had different radar suites and locations as "completed" (not necessarily as delivered). USS ATLANTA and SAN DIEGO had the SC-1 radar antenna mounted on the foremast and no SG radar. The second pair, USS JUNEAU and SAN JUAN, had the SC-1 antenna moved to the mainmast and a SG antenna installed on the foremast. (JUNEAU's SG radar set was installed at BosNY shortly after her 1 June 1942 completion at NYNY)

Also, and I'm not absolute on the Beth-Quincy units, but ATLANTA had four Mk 44 directors and JUNEAU only had two Mk 44 directors. Not sure about SAN DIEGO and SAN JUAN, but it appears in photos that SAN DIEGO had four Mk 44 directors and SAN JUAN had two. Only a limited number of the Mk 44 directors were made in anticipation of better directors would be available (aka Mk 49). Development of the "new" directors were protracted. But, because other ships had priority for Mk 44 directors, like Aircraft Carriers and cruisers already in service with quad 1.1-in mounts, the USN ran out of enough directors for USS JUNEAU and I assume USS SAN JUAN. During SAN JUAN's repairs to her forward 5-in mount at PHNY, in September 1942, she had Mk 51 directors installed for her quad 1.1-in mounts. The other three never had Mk 51 directors for their quad 1.1-in mounts.

Also, USS SAN DIEGO in February 1943, had a SG radar (SERIAL #55) and antenna installed on her foremast, below the SC-1 radar antenna. The SG radar came from the damaged USS MINNEAPOLIS.