Three body parts can be changed into three other body parts by changing one letter to an E and rearranging the remaining letters.  For example, CALF can change into FACE by changing the L to E and rearranging the C, A, and F. The three body parts and the three they are changed into are all visible.

Answer:

1. ARM...............EAR
2. NECK.............KNEE
3. HAND.............HEAD 

Credit: Will Shortz
NPR Weekend Edition Sunday Puzzle
Feb. 20, 2011