Left-handed people's body maps in the brain cortex (remember the picture of where different fingers' sensing neurons are side by side in the brain?) are the same in both hemispheres of the brain. Right-handed people have more cortex reserved for the right hand than the left.
When researchers had people hold out their arms while the researchers ran a tape measure from the subject's shoulder to fingertip area, the subject had to tell by looking when the end of the tape was at the end of the fingertips. Right-handed subjects got the right hand correct but thought their left arm was shorter than it was. Left-handed people got both right. Right handed people also mistakenly thought their right hands were bigger than their left and that they could reach farther with their right hand than their left.