A thought on Naval Gunfire Support (NGS). The US initially developed the 8" MCLWG, the Mk65 and Mk66 single and twin high rate of fire 5" to replace the NGS capability provided by the WWII vintage 6" and 8" cruisers but these projects were cancelled in the late 60s early 70s. My thinking is to fill the gap the USN selected their best remaining all gun heavy cruisers and gave them an intermediate rebuild and modernisation to serve into the 80s and possibly 90s.
This rebuilt would be aimed at economically retaining their 9 x 8" guns, while improving their self defence capability, reducing manning requirements and reducing obsolescence. The Mk38 5" twins would be replaced with Mk13 fore and aft, and with Mk45 port and starboard, four missile fire control channels, 3D radar, additional power generation and upgraded 8" mounts.
So, you're really looking at a more modern version of the Boston-class CAGs?
The Mk 13 was a single arm system and the cruiser conversions all used the twin armed launchers to provide a better PK. The Mk 45 is a submarine based launcher for Tomahawks. Did you mean the Mk 25 BDMS Sea Sparrow box launcher, the Mk 26 twin-armed launcher for Standard Missiles, or the Mk 41 VLS, perhaps?
One of the biggest concerns with the conversions of the old cruisers were the high crew counts translating into brutally high operating costs, even by 1970s standards.
For a nominal 1975 major refit conversion of an American heavy cruiser hull that was meant to retain significant shore bombardment capability (and disregarding cost entirely) might I suggest the following?
A Baltimore hull.
Re-engined to gas turbines - 3 x P&W FT4s would provide the equivalent 120,000 HP needed to retain a 33 kt top speed and greatly reduce the engineering crew required to run the ship
Deletion of all twin 5" mounts
Deletion of the aft and B-turret triple 8" mounts - Modern gunfire support really doesn't need nine 8" guns. Three is more than enough.
Retention of the A turret but modified to use the autoloader of the 8" Mk 71 system for each gun in the old turret.
Addition of two Mk 26 twin-arm launchers aft in X and Y positions with 80 rd magazines for each launcher along with target designation radars on the main mast.
Addition of two Mk 25 Sea Sparrow box launchers amidships firing to each beam and being rearmed from magazines aft in the rear deck house.
Addition of two 5"-54 cal Mk 45 turrets forwards abeam of the bridge in the old forward twin 5" mount spots.
Addition of four Mk 143 quad armoured Tomahawk box launchers right aft
Addition of two Mk 141 Harpoon launchers on the old 8" B-turret mount.
By the late 1980s they would have undoubtedly picked up a CIWS or two, one right aft and one on top of the bridge.
By the early 1990s they would have had the Mk 25 and magazines replaced by a reduced superstructure amidships and probably 32 Mk 41 VLS cells holding VL-Sea Sparrows. The rear Mk 26s would probably be retained as they would already be firing SM-1s and probably SM-2s by the 90s. But any refits in the 90s would possibly change out the Mk 26s for a much simpler 48 cell Mk 41 farm with a selection of SM-2ERs and Tomahawks, replacing the Tomahawk deck box launchers.
Replacement of the engines, gun turrets and crews and other WW2 era manual systems with the more automatic systems of the mid 70s through 80s would have undoubtedly reduced the crew from the unsupportable 1150 of a wartime heavy cruiser to a much more reasonable 300-400 of the then-new Tico-class cruisers.
These would have been very heavily armed for cruisers in the 70s and 80s and you could save a ton of money if you were to designate them purely as gunfire support vessels. In which case you could get rid of the aft Mk 26 mounts and magazines and radars and electronics as well as the 8" turrets and possibly added another four Mk 143 Tomahawk launchers right aft, possibly freeing up enough space for a helo pad and hangar for a Blackhawk or the like in the aft superstructure/Y-turret space.
You'd keep the two Mk 25 box launchers and their designators as self defense. A 1990s refit could still replace them with a VLS farm, but possibly bigger, say 60 cells adding back the SM-2 missiles and adding area air defence capability for the 90s and beyond.
Big ships provide a big canvas upon which to WHIF...
Paul