The Yosh pistons were very smoothly cast on their skirts by comparison. Their rods were lighter, and usually weighed EXACTLY the same in a given kit, with a hand-finished appearance, numbered and with corresponding wrist pins, also numbered: very meticulous. The American rods were often tenths of a gram apart in weight, usually with as-cast finishes, wrist pins in a plastic bag together.
We always shot-peened the American rods at the machine shop next door, just in case... 
Hondaman, in the interest of shedding some of my substantial ignorance, what did the shot-peen do for the rods? I'm guessing it was to clean up and smooth the finish? Did this improve strength or uniformity (or balance, I suppose)? Great discussion, by the way...
Shot-peening of metals destresses the outer layers of the metal. When metal is cast in a mold, it invariably comes out with tiny pits and irregularities: these discontinuous surfaces create local stress points, unevenly, over the surface. If put under enough stress, the metal will crack, starting at one of these little dimples.
In addition, specifically on R/C's Honda rods of the 1970s, the flashing removal process (where the mold halves met, like on typical plastic model parts) appeared to be with a grinder of coarse grit. This leaves little swipe grooves across the ground areas, which are stress points (called "stress risers") where cracks could start. The shot peening would hammer the tops of these tiny ridges down toward the bottoms of their grooves, evening out the surfaces. This reduces the stress points, or "destresses" the surface, so a bending moment has less of a place to start a crack. Even Honda's rods have this, but not as pronounced.
If you ever polish a part, you will see the irregularities right away. Polishing rods (like MRieck says) is a great way to find these spots, and do something about them. This "something" can be as simple as firmly tapping the ridge down with a ballpeen hammer, or if it is a groove or dimple, tapping the surrounding area down to that level to even out the curves. Even this little bit of hand action can have surprising results on strength.
Besides, polished rods have less aerodynamic drag, and at the speed these rods can fly, that is actually important! Fitting a windage tray in the crankcase of the 750 engine helps at extreme RPM, too: like in the 16k RPM engines I saw (and helped with) in the midget cars around Blandinsville and Macomb (750s, minus their transmissions).
So, the same general "smoothing" rules can apply to crankshaft counterweights to reduce drag and increase surface strength: on those unique engines, the c'weights were narrowed a little and streamlined (no right-angle steps on the sides of the weights, but blended in long radii), shot-peened on their surfaces, and polished with 150 grit emery paper. The windage trays were spaced .060" from the weights, but always showed scars, indicating just how much these cases can flex!
