You can then triple check by examining a kit you know is correct, like the 1/350th scale Spruance, etc. As for Tortuga, I'm only going by her stated length on the Lindberg website and her stated length which they put at 19 inches. If you enter her real length and plastic length and click calculate it shows 1/288th as the proper measurement. But - I have not picked up a Tortuga yet. But my LHS has one.
The Tort's well deck inner workings, bulkhead detail, etc, appears to not have changed much, comparing the photos of Pearl with Anchorage and other earlier LSD's. So THAT in itself is about 1/3rd of any LSD project. Don't know if I ever showed you, but I did the same thing with my 1/700th scale USS Trenton. She started life as the Airfix 1/600th scale HMS Fearless.
All I did was chop up her bridge to match USN stuff and add Skywaves spares and a scratchbuilt mast structure. As the Whidbey Island Class and Pearl Harbor all have helo decks over their well deck, I shouldn't think too many discrepancies would show through, ha ha!