That is a very unique bulletin and it also came with an announcement of the build date and proposed equipment. I have that exact one, and it was meant for dealers who were intending to buy and sell these cars. They also came with the car upon sale. The bulletin is a description of the D/Dart, and special equipment. It is also a service bulletin describing what is needed to prepare the 273 D/Dart for competition in not only D/stock, but /MP, /FX and Gas. It is not a laundry list to convert an ordinary 235 hp Dart into a D/Dart, but it was used for that purpose.... I have that same bulletin because the guy I bought my Dart from did exactly that. I have the cam, valvesprings, intake, spacer, and Holley carb from a D/Dart that were used on my car. Plus he fabbed a BUNCH of hop-up tricks like a bizarre oilpan ect.
When the D/Dart was built the smallblock was relatively new on the performance scene, and these tech bulletins got the word out pretty quickly.
The '68 Hemi Superstock cars came with a similar set of bulletins.