Yes, lets go fore to aft and hit the biggies.
Forward of the bridge on the same level as the 52 mount, you need to add twin 40mm tubs and guns (port & starboard). MK51 Directors on bridge wings
Forward Stack -- new platform to carry the searchlights. Moved from aft stack
Aft stack -- new Mk51 director tubs port & starboard
Aft stack -- main deck clipping shacks supporting twin 40mm tubs and 40mm guns (P&S)
High tub between mount 53 & 54. New "D" shape tub with MK51 director tub. Twin 40 mm
Break between midship and aft deckhouses -- 5-inch practice loading machine
Fantail -- oval 20mm gun tub with two guns. Nautilus' tear-drop shaped after gun tub is for a 40mm and was only on a couple of early round bridgers. It was too wet to use a 40 mount
Waist -- two 20mm guns each P& S
Each 20mm gun needs 1 - 2 ready service lockers
After my post I looked at a photo of the Trefthen and this is my assessment of the necessary armanent changes