Joe, the correct "factory" smog pump for a 1968 L26 230/140 6 cylinder (or LF7 V8 327/210) engine with the base 3 speed manual transmission is P/N 7802609.
After production ended and service took over, one part number was supplied for multiple applications. In this case, as referenced in your August, 1972 book, it's P/N 7806686. However, in the September, 1968 P&A, it was P/N 7803947, and it covered the 68 Nova, Chevelle and Camaro with all engines, so you can see that a lot of "manufacturing" part numbers were serviced with just one!
The picture you have and the highlighted part is for P/N 7817807, and it was for the 1975 Vega and Monza. The 68 and 69 listing you have highlighted is missing the part number.
If you're looking for a smog pump, you'll have to find an original 7802609 with the correct date code on ebay or swap meets, or if the numbers don't matter, just find one at your local auto parts store.