Why not look for an MTH 2R [ = scale wheels in MTH-speak ] Pacific -- either the complete loco, or ideally just what you need. Granted, it requires patience, but since you're going 2R you'll need that sooner or later.
I would think the internal layout would be very similar -- but I have been known to assume that in the past, and be wrong, especially since MTH's Chinese designers seem* to want to reinvent everything but the wheels [ and sometimes those also ] with each different model.
*Perhaps I should use the past tense now....
EMD: Every Model Different