Looking at a 68 GTS.......

You can see the basic layout at http://www.hamtramck-historical.com/images/TSBs/1968/D68-25-1 page5.jpg

In addition to that though, you also need to know what the sales codes are.

I can read '69 up tags like a well written page.

1968 back tags give me a headache.

Great, got the codes from a GTS Registry link, so can at least confirm engine, trans, suregrip, and a few others.

1968DartInvoice.jpg