Yes, the wheelbase of 6 m fits Linz type car, but don't overload it, please!
30 tons is too much. 25,5 tons was the max load weight (officially at least, although on the car boards plain 25 tons are stated). This wheelbase fits also the rest most used open cars back then, of Villach and Klagenfurt types. More on this offline, no need to annoy the public here.
Talking about the rolling stock availiability I'll say this:
1. I know Dragon used to make some German freight cars in 1/35. Frankly, looking at the pictures of built ones, I'm happy they didn't launch them in 1/72 too;
2. I also know 1/87 is the best scale for such things, being a genuine railroad scale. BTW, many good AFVs and softskins are available in this scale by different manufacturers but they are traditionally overpriced. At last but not least, it is too late for me to change the scales at this age
3. Planet/CMK railcar kits I'll comment with 3 words only: gorgeous expensive crap. Really useless.
Yes, what I have done and what I think to do from now on is planned for my own use and not for sale definitely. And for your use, perhaps, but you must be patient till my new batch of RTV will arrive. My RTV stock went belly up again, that's it