I am trying to make a silk purse out of a sow’s ear, and I need decent ordinance before I proceed. Who makes’em and what kind of procurement tag do I need to get them on my boat. (Revell 1/72nd PT-109) And who might also have torpedo tubes and different boat #'s? Swab, get that ropeline secured!, sorry new man on my deck.
White Ensign Models has it all.
http://www.whiteensignmodels.com/acatalog/index.html
Fret 1

Fret 2

The 50s are on this fret. They include a complete carriage system (almost functional). The gun sides are PE appliques and roll the barrel from the perforated piece
37mm AT gun

37mm Oldsmobile Cannon

20mm Oerlikon on pedestal base

This is for the Revell Gato. The 20mm which is included in the PT-109 kit is pretty good, and WEM’s PE set has detail items to improve upon it. This is not necessary unless you have excess money burning a hole in your pocket.
Edit
oops! forgot the roll-off torpedo racks. These come with resin Mk13 torpedos

Roco Minitanks made a U.S. 37mm field piece that came with a (jeep) trailer that was pretty close to 1/72nd scale (1/87th?). Don’t know if they still do.