Here's the Design 507, a 4000t scout cruiser drawn up in March 1940. It comes in two flavours, one armed with twin 6"/47 DP mounts, and an alternative with twin 5"/54 DP mounts. It has 8 Browning M2s for AA and twelve torpedo tubes in four triple launchers. For scouting it has two SOC Seagulls that were to be launched with cranes, there were no catapults. Top speed was 35kts and armor protection was minimal, and limited to the guns and engineering spaces.
6"/47 variant:
5"/54 variant:
I'll throw in these that I've been keeping for long enough. These are two Iowa class preliminary designs, one for a 30kt fast battleship armed with 9x16"/45 Mark 6 guns on a lengthened South Dakota style hull. The other is a slower 27kt heavily armed, and heavily armored ship with 9x18"/47 Mark A guns, also on a lengthened South Dakota style hull. Despite being labeled as 55,000t it's standard displacement was 45,000 in keeping with the treaty escalator-clause.