The 10-tooth pinion and 25-tooth intermediate gears look like stock Lionel gears. Some of the genius in this mod is precisely locating the studs to achieve the proper mesh. The intermediate gears can't practically be any larger (or any closer to the rail head), because you would encounter some of the known problems with prewar steam and "fat wheel Marx," i.e., the gear teeth will contact the guide rails on switches.
It also looks like the wheel bearings (bushings) were carefully adjusted to protrude slightly, so that the backs of the wheels don't rub on the larger intermediate gears. I doubt Lionel installed them that precisely at the factory!
It seems like redoing the studs would be easier with a 2028-100 truck block. And that's generally regarded as a better quality drive than the sheet metal 600's. I respect this man's skills enormously, but my personal preference would be no tires. Just add weight, or better still, two powered trucks. (For a dual-motored setup, you would have to start with a 2383 truck block, because it's recessed on the underside to accept a pickup roller.)
Personally I'm sick of "speed control" and all the failure-prone electronic gimmicks. With a home-sized layout I don't need to go more than 50-60 mph, so I'm convinced there's a market for mods like this. Hopefully this isn't the last we'll hear of these mods!
