the regular 22/45 comes with a under rail if you get the model 10149.
none of the 3 22/45 Lites come with under barrel rails.
so you would have to drill and tap your barrel to put a rail on it.
that or get a threaded 22/45 barrel from a 10149 model.
seems like a lot of work when you could just but a model 10149.
same frame, same size, both threaded.