SHEDDEN, ONT. and TORONTO — A long-simmering rivalry between criminal biker gangs appears to have exploded in the largest gangland slaying in Ontario history. Three members of the Bandidos motorcycle club, long-time rivals of the Hells Angels, were reported missing Friday and may be among the eight bodies discovered Saturday morning. One of the missing men is believed to be associated with Superior Towing, the Toronto-based company whose truck was found abandoned on a side road south of London, Ont., not far from the home of a well-known biker-gang leader.