You can find some excellent drawings for the Baltic tanks in this thread that I created some while ago. http://www.rmweb.co.uk/community/index.php?/topic/97273-bcdr-baltic-drawings/
I remember very clearly putting together a list of parts to create a accurate running chassis, but it would have cost me £70 and that's without any motor or gearbox, so i gave up haha. The body will have to be scratch built, I don't think there's any viable way around it. If anyone is interested, correctly sized wheels can be got from scalelink.