Bachmann
will sell you a part, but it has to be listed on there website. I know it suxs.
I don't know what years 344 had the plow other than 36. And yes she is also equipped with a flanger. Thats what the air cylinder is for.
The steam dome lid could have been changed for any number of reasons. Like someone dropped the flared lid and broke it and replaced it with what was around. Who knows,but things like that are what make NG so interesting.
I have seen a picture of 341 with two 9-1/2" pumps.
Second air tanks are nothing special to c-19s. Many locos had them c-16s,17s,18s,19s even the c-25. I don't know when they installed them or to what engines nor do I know when or if any got removed.