can you fit other rods/gear to the 4-wheelers? that sounds like an interesting 'kit-bash'
Well it depends. After the 1655 ceased production in 1949, none of the Scout/Columbia locos had connecting rods, until Lionel elongated the boiler and turned it into a 4-4-2 circa 1984. To add a connecting rod, the driving wheels have to be pressed on "in quarter" and the gears have to be timed correctly. For example, the holes on both axles have to be at the 6 o'clock position. Both sets of wheels have to be tapped to accept a hex bolt to retain the connecting rod. You could cheat by using the mechanism from a 1615 switcher (all of these had quartered drivers and full valve gear.) But you might have to swap E-units to get the lever to fit into the Columbia body shell. I would have to look at the service manual and parts lists to see if the wheels and rods are fully interchangeable with the 2034 and 250.
I don't personally mess around with plastic Scout motors. Even the Lionel service manual suggests replacing the whole motor/chassis with part number 250-100.
One more note for those who might wish to build their own "super Scout": Although not strictly postwar, when General Mills / MPC took over Lionel in 1970-71, the ONLY steam locos in the product lineup used a redesigned version of the 249-100 four-wheel motor. This MPC motor had some improvements and some drawbacks compared to the 1950s metal Scout motor. Most importantly the armature is MUCH larger in diameter. In fact, it's the same size as the armature that had been used in six wheel drive locos like the Hudsons, 2025, etc. It also has a much thicker stack of laminations than the motor in a 244, 247, or 249. So in theory, the MPC motor should produce more power and torque than a 249-100. By virtue of its larger diameter, it definitely provides more coasting. The mounting points are exactly the same, so it's fully interchangeable with a 249-100. The variation used in the MPC-era 4-4-2s like 8142, 8204, etc., have all wheels tapped and the drivers properly quartered to accept a connecting rod. But the hex bolt is a different size and thread than postwar hardware and the rear wheels have a "boss" or shoulder to accommodate a new driving rod design. The downsides, the MPC motor is a bit lighter in weight. Most of these have a single grooved wheel, and long-wearing rubber tire. If you want the larger armature and field, you'll also have to live with nylon gears and the shiny aluminum sideframes, although I've seen at least one case where someone painted the sideframes a dull black for greater realism.
The corporate budget must have been tight in those early MPC years. I always wondered why they went to the trouble of redesigning something that worked pretty well already. And being as they did, it's a shame they didn't also gear it down for more realistic speeds. Good topic!