The gearboxes are available direct from the guy that makes them. His website is here. They take about 5 hours per side to assemble, but they really pull a KT and JT around nice (20 and 22 pounds respectively). Willy L. also sells some really nice gearboxes too that are some heavy metal.

I hear you on the electronic expense...lol.

As for your Lowe, it might be a plausible alternative if you were to Ebay your Tiger chassis, and just buy a used KT. You'd get just about everything you need to build it. As for the wheels, put some consideration into how much this beast will weigh when finished. Metal wheels are really no better than the plastic ones (i.e. functionally speaking) but they add alot of weight. I've had them, and sold them off to replace with plastic ones....The metal tracks and the resin upper will add alot of weight too...not to mention you'll be stretching (I think) the KT chassis a bit. You'll be lucky to finish it and be under 22 pounds. I'm not saying forego the metal wheels...just know it's a slippery slope once you start adding metal parts...the KT chassis gets heavy pretty quick.

Still, it sounds like a very cool project. It will be the only one of it's kind.