I dug out my K27 drawings and found the following:
The width across the frames is 56".
Centerlines of the cylinders is 80"
Adding the width of driving boxes and counterwieghts, adds 10" to each side, plus the width of the side and main rods (another 12" total). The total distance across the running gear is 100".
To make the frame side members work, you have to reduce the width across the frames to about 30 1/2" (from 56").
The centerlines for the cylinders don't move in much, only a couple of inches,assuming the new drivers are about the same width of the old counter wieghts/cranks.
However the cylinder saddle is designed and machined to fit the frames and become the front cross member of the running gear. You can/t simply plop the old casting on the newly narrowed frame, and make it work. A new cylinder saddle would have to cast and machine to fit the narrower frame. The vertical plane of the cylinders/valve gear moved inward enough to require a new valve gear hanger as well.
Here is something else it just discovered: K-27's used a separate front frame extension from ahead of the #1 driver through the cylinder saddle, over the pony truck and to the front pilot beam. There were different front extensions designed as the cylinder were changed from compound to slide valve to piston valve. So, a new front extension could have been made to accommodate the original cylinders with the narrow frame. I would think making the frame stresses make two 90 degree bends from the pistons to drive wheels, would quickly break the frame.
Maybe.....