Sov has to upgrade and feed its army for 5 years before the war. In their case it might still be a good idea to disband all obsolete land units (i.e. most of them) and build from scratch. The IC days going into your army will be ridiculous for not having to build any or almost any supplies for about 3 years. Rush infantry '39 as early as you can spare a TT.
Edit: Keep or train enough to smack the Finnish around, though.
Edit2: I think SOV has or had a lot of cavalry divisions, many of them '32 and '36. They won't fare as badly in FIN as they should.
Also, 30 divisions in every province? How? I once attacked the Soviet Union with Poland in 1947 for the lulz, and they didn't have 30 divisions in every province. More like 15. I had nothing of the sort, even though my Poland was heavily buffed with cores in Prussia and Silesia and 3 puppets beating Germany and getting a nifty, custom peace event. So they still handed me my own teeth.