Yep. The winning suggestion is to add a tether to the tender. Four pickups are better than two, and easily removable if you want to put it back to original.
The 229 is the same loco with slightly nicer Baldwin disc wheels and roller pickups, which are spaced more widely than the sliding shoes on your 1664. But if I were going to explore the notion of swapping motors, I would look closely at the motor from a 1656 switcher. Roller pickups and double-reduction gearing for smoother running, plus no more "fat wheel" syndrome. (On single-reduction motors like your 1664, the gear cast into the back of the wheel is the same diameter as the wheel tread. This causes derailments and clunking on some other types of switches.) Problem is, a 1656 motor isn't a bolt-in swap... To reuse your side rods, you would probably need to pull and press all four wheels; I don't know whether the axle diameters and gear tooth pitch are the same. If you managed to succeed, a 1664 with a 1656 motor is pretty much the ultimate 2-4-2! I love these locos so much, someday I'll buy a bunch of junkers at York and give this a try.
@Steamer your 1664 is a Franken-loco. It looks like it's been remotored with the chassis of a Postwar large Hudson or 2018 Prairie-type. Definitely effective but an entirely different beast.
