I know Miniart does an excellent Valentine, so thats sorted out.
Im thinking I can do a Tamiya Churchill mk IV, and paint it soviet colours. I think that will suffice.
The Matilda is the hard part. As far as I know, Tamiya is the only company making Matildas. I havnt found any information on whether the Matilda III/IV was sent to the Eastern Front or not. If only ICM had released the specially made soviet matilda....
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As for the Universal Carrier, Tamiya makes a MK.II which I think should be sufficient.
http://www.youtube.com/watch?v=Q1GWwRr-Uyc&feature=related
I am also guessing this video is slightly false, as no Covenators or Crusaders were sent to Russia......