When ACG added PullMore wheels to their steamers, it was actually a major production change. This is because the PullMore wheels are actually larger in diameter--just the wheel rims though. However this also meant they had to take off some of the rear chassis mount "flange" on the engine base to clear the larger flange diameter. So, to add pullmore wheels to a steamer also requires changing out the front plain wheels too-or at least their tires, otherwise the locomotive sits Nose-heavy, and the pilot will strike the rails when the grade changes to go up a trestle. Not checking driver diameters is also why some repaired locomotives rock--one wheel is different (larger or smaller)! the center wheels are flangeless, and seldom touch the rails, so they don't have to be changed.
If you have problems quartering drivers (there is a quartering tool out there, BTW) it might be easier to find a later chassis for your locomotive and do a "heart transplant."