Very, very nice. I wish I could build like that!
One small note: your road wheels and idlers are incorrect at the moment. You now have the early road wheels and idlers with only 5 bolts instead of 10 as used on the IS-3M and also the ISU-152K. See this link for a picture:
You can add the 5 extra bolts or you can use the wheels from the Trumpeter IS-3M kit but the Tamiya wheels have better detail.