Frank, you'll need Minitweaker and you'll need the sub.guns tweak file.
You can get the tweakfiles here -
http://www.savefile.com/files/684634
You can get Minitweaker here -
http://www.delraydepot.com/tt/sh3sdk.htm#tweaker
Tutorial on using Minitweaker -
http://www.subsim.com/radioroom/showthread.php?t=110889
I don't even play SH4.