Any era, any scale caterpillar tractors, for example Komintern, Voroshilovets, YA-12, Komsomolets, RSO, M-4 high speed tractor. Main destination of tractor is towing the gun and it crew. So, no modifications of RSO with PAK-40 or Komsomolets with ZiS-2.
Start date and duration is subject for discussion.
PS I have Komintern and Voroshilovets in my stash and thinking about Komsomolets and STZ-5
Start date and duration is subject for discussion.
PS I have Komintern and Voroshilovets in my stash and thinking about Komsomolets and STZ-5