Phil,
I have not personally, and I know that Dick hasn't been to NARA II so he can't, have reviewed in person what paper drawings that NARA has for the CLEVELAND class. I have gone through many paper destroyer plans at NARA II and they can be a mixed bag. Most are blueprint BGP copies, but sometimes there are original mylar drawings used for making the blueprint BGP's. Also, other plans turn-up in files for a ship that may be useful. Pre-WWII ships had what are called "Portfolio" (PORT) Contract Design drawings used for sending out with requests for contract proposals and the drawings are pretty detailed. Many times these drawings are early and don't reflect what gets built many months later. It looks like the CLEVELAND class don't have PORT drawings ...
http://archive.hnsa.org/doc/nara/shippl ... folios.htm ... HOWEVER, I notice that this list doesn't show PORT drawings for FLETCHERS and I know those exist because I have copied them. Also, other random plans are found in the "paper" drawings. The only real way to know is to go through every ship file in the class to find out. With some 24 ships in the class, that could take awhile with each Pull (about 4-5 pulls in a day) limited to ten drawings each (one BGP counts as ONE, but each original paper drawing "roll" counts as ONE as well). When I was going through destroyers, it took me several trips to get through ALL the FLETCHERS (175 ships, but there were not drawings in their collection for ALL of them) and some of the other destroyers folders. Normally the "engineering drawings" for individual ships are only available on microfilm ... which you say you have already been to. Why drawings would be missing, I don't know.
I can't give you a better idea of what is available until I can look in the master drawings lists at NARA in reference books they have there (I have NEVER had much luck looking on-line through NARA files via their system ... I can't even find things I KNOW that are there and WHERE).
I don't know what may be available in BuShips Textual records.
I have not tried looking for gun mount drawings. These would be under Ordnance rather than BuShips files, so I'm unsure where they would be located. I see from the listing on hnsa ...
http://archive.hnsa.org/doc/nara/shipplans/ordnance.htm ... that there should be drawings available at NARA for the guns you are looking for.
The good thing, is that scanning of paper drawings in digital format is pretty reasonable at NARA ... paper copies is another matter!!
You can try to hire a pro researcher, but that can be pricey, the best way is an in person visit to NARA. Depending on the skill and knowledge set of the pro researcher (some have no idea of drawings), a lot of time is spent on their part (and the meter is running) learning and back-and-forth with YOU trying to get to what you want. I know that getting to Maryland from the West Coast can be expensive, but a week long trip would help on your quest and even if you don't get everything in one trip, you can narrow down your focus of requests to a pro researcher and/or direct requests from NARA to get the balance.