You could easily get a Burke forward 32 cell arrangement in there.
I'm going to regret telling you guys this, but I've given hints of it in the past so here we go.
You can easily fit a full 64 cell Mk 41 package into the barbette of a Montana. The VLS package is 343 inches by 249 inches, which gives a corner to corner distance of 423 inches. The barbette inner diameter is 447 inches. This gives you about a foot for structural supports and clearances on each corner.