Sabot,
You are right about the JS-3. I was mistaking it for another model. I went and looked at my kit and it doesn't have motorization holes. You are alos right about it being based on a bizarre one-of-a-kind hybrid vehicle. As I remember the rear engine deck is that of a T-55 and not a JS-3. The vehicle is in a Russian museum and they rebuilt it with the T-55 engine deck because they couldn't find a real JS-3 engine deck.
In regards to Trumpeter, their early kits sucked, but their newer ones are pretty darn good. I would typically pcik a non-motorization hole Tamiya kit over any other of the same vehicle, but with the JS-3 I would pick the Trumpeter kit over Tamiya because it builds up just as nicely and it is more accurate.
In regards to search engines, besides Squadron, ,go to
www.greatmodels.com. I wouldn't recommend buying from them unless you are tolerant of quirky service, but I have found that the search engine on their site is the nicest of any other vendor. Just go to their site, click the "Database" link and type in "T-70" or whatever and a whole list of stuff will come back including referencee material, models, and AM stuff.