I am not a 3RS person nor do I model the N&W, but I "have" to ask this question:
How close dimensionally is the MTH fishbelly hopper to the Atlas N&W one illustrated above ? I note the basics [ ribs and location especially ] look the same. If it is close, why not just buy those and add the peaked end ? One could obviously upgrade the details as one saw fit in the process.
A very quick look at the MTH website shows that there are a ton of these cars in different road names and colors available now, especially in six packs. Repainting and decaling would finish them off; one would have to do the latter to get different numbers anyway. And no need to put KD's on every car; make blocks of three to five cars, say, and use scale dummy couplers within.
Just wondering.....
Best, SZ [ who used to run Williams ( remember the white plastic kits ? )and other hoppers through his table saw ....]