Might even be best to use itty-bitty Palstruct C channel--even though the prototype would have an "E" sort of section. Which would be about 2.5-3" wide with a ±1.5" rail in the center. That 3" being 0.009" at 1/350 (1/32" channel being about 10" wide to scale.)
American standard rail gauge is 4'-8-1/2" inside to inside, which is 0.16" at 1/350. That's a shade over 4mm, ZZ scale track, at 4.8mm would be a skosh wide for that, but would look good in the non paved areas for being 1/300 (what a person would do with the left-over Skinkasen could be interesting)
The crane tracks (which are also set flush to the pavement) are about 8' to 10' wide, using my potentially faulty memory, and use tracks separate from those used for rail cars. That would be 0.27" or 6.9mm to 1/350 scale.
HO is 1/87 or about 400% too large for 1/350; N is 1/160, about 200% too large (but, not bad for 1/16" = 1'-0" or 1/192 scale if done carefully).
I know I've seen a dio of that dock with CSS Virginia being made from USS Merrimack--but, danged if I can remember where. And it was a handy way to gloss over having to guess a bit on the hull form. Since we have a reasonably-good knowledge of the South Dakota's hull, I still kind of think a sort of half-section of the drydock would still work handily.