Yeah, with the Intermountain release those mini-kits are probably worth their weight in resin.
I recently completed the NYC USRA offset side conversion. The castings weren't too bad. I used a Tichy hopper (not an Accurail car as recommended) and the process went well, although the decals supplied by SS were horrible. Very fuzzy. I ended up decaling the car letter-by-letter and it took forever.
I believe Martin did a MP hopper-top conversion. If you've got that one and are letting it go, can you give me a shout, please?