Open the .cat file which consists your needed TShips file (13.cat for Vanilla 3.1, or the .cat of a used mod) with X³ Editor 2. Select and open the directory "types" inside the .cat, and there left click on "TShips.pck" (if there is none, you've got the wrong .cat). Select "Open with..." > "Text Viewer".
Now you'll get a new window which shows the whole TShips file. Select and copy the whole text, and paste it into the textarea of my above linked website. Afterwards hit [Process]. After processing, select and copy the whole text inside the textarea again. You can ignore the Debug Information beneath. Paste the copied text into a new simple text file, e.g. with notepad or a similar programm.
Save the file as "<path_to_X3TC_root_directory>/types/TShips.txt". As far as I know, your game should recognize the new file after the next start of your game, as files placed like that should have highest priority.
Anyways, you also could pack it as a .pck file (use 7-zip or a similar programm) or you could even pack it into an own .cat/.dat file (again, use X³ Editor 2 for that task).
But thats eye candy on the one hand, and more important for distribution on the other hand.
... didn't had time to post that description during work ... first off, I'm going to sleep now
