This Catalog 17a has a copyright date of 1975, and is generally considered to date from late 1975, describing the range for model year 1976. However the first fly sheet does include the information that Campagnolo is the sole technical advisor to the World Championships in August 1977 in Venezuela. Presumably this had been arranged two years in advance.
In terms of derailleurs, the main change from Campagnolo's catalogue n. 17 is the return of the thoroughly underwhelming Campagnolo Velox (2250) and Campagnolo Gran Turismo (2270). So it describes a line-up as follows: