Yes the USS MUSTIN August 1945, Anti-Kamikaze configuration was the last one for the SIMS class. As it was, MUSTIN was the only member of her class to actually receive the mod. The SIMS class survivors were part of the "now obsolete" pre-WWII built destroyers declared surplus at the end of WWII and were disposed of. So no other surviving units (five units out of the class of 12, were lost during WWII) were given any upgrades post-WWII when the sisters to MUSTIN returned to stateside.
Yes USS WAINWRIGHT with three single 40-mm guns was a "one-only" conversion. When the German Air Force made a determined effort in early 1944 to attack the allied fleets off Italy and around the MED, the "temporary" addition of more AA guns was authorized on a DesDiv basis for such units assigned to operate in the MED. Destroyer Divisions 13, 14, 21, and 25 were so authorized as were many DE's. All of these were early BENSON-GLEAVES units except for USS WAINWRIGHT, the DesDiv Flag for DesDiv 25, making her the solo SIMS class unit authorized with this upgrade.
On the BENSON-GLEAVES class units, a temporary platform for four additional 20-mm guns replaced the aft torpedo tubes bank. An additional and separate mod authorized a pair of singe 40-mm mounts added on the main deck aft of the temporary platform and ahead of the two twin 40-mm mounts. In total at least 15 BENSON-GLEAVES class units received the platform for four 20-mm guns and at least 13 units also had the two single 40-mm mounts. The augmented armament was installed at either NYNY or by USS VULCAN (AR-5) at Oran. Few photos exist of these units so armed and verification of some units listed in Armament Summaries can't be verified with a photo(s), particularly for the difficult to see single 40-mm mounts, only via textual records.
The best set of images I have come across, are of USS NIBLACK (DD-424). A series of 14 March 1944, aerial views shows her after the temporary platform for four 20-mm guns was added. See first image. Then another series of photos taken on 9 April 1944, shows that the two single 40-mm mounts have been added, requiring the relocation of two K-Guns further aft. See second image and third close-crop image from the same photo.