Usually the conversion is done so that the completed rod won't use shims
Agreed- - - -we would usually machine/hone the rod conversions to a specific diameter without shims in place. With the rods torqued to 35-45 ft./lbs. the rod bore should be 2.4030"-2.4040". That should allow the insert bearings to run the proper oil clearance. If the clearance exceeds .003" the bearing is worn out and should be replaced. Insert bearing are currently available in .010" and .030" undersizes. The .020" undersize bearings have been unavailable for a long time. My friend who runs a machine shop has been searching for .020 under 216 bearings for a couple of years with no luck whatsoever.
Rod bearings for a Massey-Ferguson Diesel tractor (Perkins engine) can be modified to work in a 216 and they're available in all the normal undersizes. There are also Komatsu and John Deere rod bearings that can be adapted to 216/235 splasher rods.
Jerry