Here are a couple of photos of a fixture I used to use to narrow Pinto 1600 rod bearings to the Cosworth "narrow" bearing width.
It was used with a large bore 5C collet normally, or an "accurate" 3 jaw chuck.
If I recall correctly, we took off .120" off the width. No idea what % that is. We only did this with Clevite 77 bearings, our first choice. Other tri-metal high performance bearings would work. Hope this gives you some ideas.
Fordboy