Bob Johnson (the M:I tape voice) did sound a lot like Bart LaRue, and several TOS voices traditionally credited to LaRue were actually Johnson, according to Memory Alpha. It credits him with the following
"The Cage" as Voice of 1st Talosian, and Voice of Transporter Technician Pitcairn.
"The Gamesters of Triskelion" as Voice of Provider 3
"The Immunity Syndrome" as Starfleet voice
I've read that Walker Edmiston overdubbed some of actor Harry Townes' lines in "The Return of the Archons." This might have been due to Townes' pronounced southern drawl. Perhaps the producers felt that an inhabitant of Landru's planet shouldn't sound like a good ole' boy. I don't believe Edmiston was ever credited on-screen for his work on TOS.
That wouldn't have been Harry Townes (Reger), but Lev Mailer aka Ralph Maurer (Bilar), the bowler-hatted fellow who first greeted the landing party on their arrival. Bilar's voice was a nasal tenor like Edmiston's, totally unlike Townes/Reger's fuller baritone. Also, his voice was rather blatantly dubbed, as were all the voices in the scenes shot outside on the backlot -- a standard practice in Hollywood since outdoor conditions, wind, aircraft noise, etc. can make it difficult to get a clean voice track. Probably they used Edmiston for the looping session because Bilar had no indoor scenes. Since every one of his lines had to be dubbed over anyway, there was no need to use the actor's real voice, and it was probably more convenient just to give those lines to Edmiston (perhaps in the same recording session as his lines in another episode) rather than hire Mailer to come in and do it.