Nautilus Models will soon be offering a couple of resin conning towers with the correct Government Tower configuration. From what James Corley of Nautilus posted on SteelNavy, the Trumpeter tower is about 2 frames too long and tapers too sharply.
The initial release includes the HADDO (SS-255) 1942. Covered bridge with cigarette deck cut down, 20mm gun, and a 3"/50. The periscope fairing is corrected and the SJ radar mast is provided. The 3"/50 gun is much improved over the kit.
Next is the WAHOO (SS-238) 1942. This is the first cut-down sail with the forward deck opened for the 20mm gun. There will be a 4"/50 gun and a TBT mount for the conning tower (I'm reading WAHOO by Dick O'Kane right now and a WAHOO set is on order.).
Also up is the TAMBOR (SS-198) 1943. This is essentially a repeat of the WAHOO with a 5"/51 gun, widened deck sponsons and some resin replacement muffler bumps for aft of the sail.
James will be releasing replacement sails for the later war Trump GATO when it is released. He is also working on a system for cutouts for the various shipyard limber hole patterns.
White Ensign is preparing a whole suite of replacement weapons, .50 caliber, 20mm, 40mm single, 3-inch and 4-inch guns.