Here is the infamous Yamaha rod kit conversion. Kit includes crank pin, special High Performance crank pin bearing developed by Hot Rods, wristpin bearing and washers. This conversion will require machine work. Extra effort but worth it.  If buying for Explorer or MAR after 1974 you will have to verify if you have a straight crank pin or stepped pin. 

Note: Machining Specs at bottom of page under "Micro Films"