John Snyder of White Ensign Models has announced the impending availability of a 1:72 scale Oldsmobile 37mm automatic cannon for use as the bow cannon on mid-to-late war PT boats. The Olds cannon originally was installed in the nose of P-39s and made it onto PT boats from salvaged aircraft. The detail set is in white metal and brass. Price is 5.91 GBP
http://whiteensignmodels.com/
See too the other 1:72 scale PT Boat details.
Not afiliated with WEM, but a satisfied customer