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That depends on the original design of the crankpins. Those with rods held on by retainers, possibly. Those with rods having split brasses in forked ends, probably not.

Room for the bearings in the rods ends is a larger issue, but for new rods new pins are probably a good idea anyhow, so..........

have you thought about floaters?

dave

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Dave is talking about floating bushings that are free to rotate on the pin and in the rod...note this requires the right grade of steel for the rod or possibly an insert of the right steel to adapt the rod.

Key considerations for any such change are the maximum speeds the locomotive will be operating at, expected thrust loads, and the underlying grade of steel/hardness of the pin...other considerations include driver diameter as roller bearings tend to be larger in diameter than the equivalent plain bearing and there needs to be enough rotating room to clear them.

See the arrangement used on the Union Pacific FEF locomotives, for example in Kratville's Mighty 800. Bruce's The Steam Locomotive in America describes the principle, pp. 218-220, with a sketch.

While I agree that it would be better to put steel inserts into the rod eyes, I'd have to wonder whether boring out the existing eyes and perhaps using a hard coating on the surface would serve properly. ISTR there has been a discussion of where any 'slack' in the fit between the eye, the sleeve, and the pin should be to accommodate the necessary freedom from binding in older, or sloppier-fitted, locomotives. If the sleeve or eye wear funny, they may seize or stick (and you then may have difficulty getting grease from the rod fitting through a relatively small number of the holes in the sleeve...