Bob and Carol's plan to kill Grant Gendell and have Bob take his place would never work. Grant Gendell is 37 years older than Bob and the actor playing Bob was only 25 years old at the time. It was a well known fact that Grant Gendell had been in hiding for 23 years, even Carol mentioned that fact, so there is no way Bob could take his place and no one would know. Anyone he met would immediately know he was too young to be the real Grant Gendell even if Bob was older than the actor playing him.