What exceptional words turn into other words by substitution and transposition of letters?

longest switchback (substitute first letter and reverse the rest) 
OSCILLATE->METALLICS (9)
longest backswitch (substitute last letter and reverse the rest) 
LEVITATORS->ROTATIVELY (10)
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Unless noted otherwise, all words occur in Webster's Third New International
Dictionary, Merriam-Webster, Springfield, MA, 1961.