Interesting. The previous catalog listed the 8820 and 8821 adapters for the front and rear of both the Intruder 1400 and 800. They fit, so I wonder why they changed the listing? Unless this is another example of the confusion caused by the dropping of the names and the swap to the S, C, M number designations for the models...
Anyway, 8820 is the adapter for the front, 8821 is the adapter for the back. Stirrups with large ISO pegs are about $110-120, less with regular ISO pegs. I had never considered them, but rode a friend's bike that had them and found them to be every bit as comfortable as the floorboards on my Electra Glide, but retaining the things I liked about pegs, so I bought a set for my Sporty. I had previously tried the ISO mini wings from Kury, but did not like them much.