I tried several years back to catalog the configuration changes for the CLEVELAND class and found it difficult. The first seven or so completed units went through numerous changes. As the authorized armament changed for the class (or sub-groups with-in the class), the changes were made unless a further change superseded it before a yard period was accomplished. The next five units went through just a couple of major changes. Yes twin 20-mm mounts were installed starting in early to mid-1945, I can't remember the number of twin mounts right now and which single mounts they replaced. The CLEVELAND class was always weight and space limited and it prevented the addition of more 40-mm mounts. I was surprised that MANCHESTER was the only one of the class to get twin 3-in mounts and then she got eight of them in 1953!!!
To really track these ships configurations will require a fair amount of work. I started by listing all units in order by commission date and noted which of four builders built them. Then I went on photo searches. I started to note when changes in configuration (mostly 40-mm mounts). After a point I gave up trying to find when updates occurred, I just didn't have enough data. I didn't even try tracking numbers of 20-mm guns mounted. To do it right, I need to spend time at NARA and I have other priorities. Here is a thumbnail of what I found.
The original "round-face" bridge units were the first commissioned;
CL-55 CLEVELAND -- 15 June 1942 -- 4x2-40mm mounts (8-40mm)
CL-56 COLUMBIA -- 29 June 1942 -- 2x4 & 2x2-40mm mounts (12-40mm)
CL-57 MONTPELIER -- 9 September 1942 -- same
CL-58 DENVER -- 15 October 1942 -- same
CL-60 SANTA FE -- 24 November 1942 -- same?
CL-62 BIRMINGHAM -- 29 January 1943 -- 2x4 & 4x2-40mm mounts (16-40mm)
CL-63 MOBILE -- 24 March 1943 -- same
The "squared-face" bridge units were next;
CL-80 BILOXI -- 31 August 1943 -- 4x4 & 4x2-40mm mounts (20-40mm)
Edit: Should be 4x4 and 2x2-40mm mountsCL-81 HOUSTON -- 20 December 1943 -- same
CL-89 MIAMI -- 28 December 1943 -- same
CL-64 VINCENNES -- 21 January 1944 -- same
CL-90 ASTORIA -- 17 May 1944 -- same
CL-65 PASADENA -- 8 June 1944 -- 4x4 & 6x2-40mm (28-40mm)
From PASADENA on all units were commissioned (one suspended) with 28-40mm guns. The last five units ... PROVIDENCE, LITTLE ROCK, PORTSMOUTH, MANCHESTER, and GALVESTON (suspended basically complete and mothballed ... not commissioned as a gun cruiser), had two of the twin 40-mm mounts relocated from amidships to the fantail. Other units had this same upgrade.