Welcome aboard, it's always good to see new members. As for your gearboxes, I would go with the v2, with the black steel gears and the bearings on all the shafts. I have a set of the V3 and I have to say I don't really care for them that much. I think the V2 is the best set of gearboxes for the money right now.

As for the smoking barrel, that's kind of a new thing that recently came out but it shouldn't be difficult to retrofit in just about any tank. It's just a question of adding the tubing and the additional smoke unit. That's something I plan to do to several of my tanks when I get to it, but right now I have so many projects waiting on the shelf that I doubt I'll live long enough to finish them all.