Marc,
As far as the gear boxes are concerned, I don't think you can tell just by the part number. If you can see the gear boxes, the newer have black covers (removed in my picture-left side). They are more durable and slow the tank down by about 30%, but it is still too fast for a Tiger. This should not be a real problem unless you planning to run it in battles with people who are concerned about 'scale' speed.
We run quite a few tigers in our club and most are stock. The metal tracks are nice, but can add strain to the entire drive train. You might want to try the stock tracks first. Some people love the suspension upgrade from wechoe, but its is a bit expensive. The metal barrel can be nice because you don't have to be as concerned with sanding the seam away from the plastic barrel. I had issues with the seam and the recoil unit that took me a while to figure out.
I will be adding Daryl Turners Track Tensioner (from ETO Armor $60). Stock tensioners have been giving me trouble, and Daryl's look much simpler and reliable.
Kevin O'Connor
<S.C.A.T.?
www.socalareatankers.com