I didn't think there was any doubt that the 3406 was offered in the 9000-series just whether it was offered in the LNT9000 as well as the LT9000. From the 1987 brochure, the 3406B was offered in the "Ready to Work" LT-9000-702, LT-9000-703, LT-9000-708, LT-9000-710, & LTS-9000-705
The 1993 brochure, shows that the 3406C was only available on the L-9000 & LT-9000:
Now, that doesn't mean that someone couldn't have stuffed a 3406 into a LNT9000 glider, or into a truck that blew a different engine.