Swapped what?

A woman went to the undertakers to have one last look at her dearly
departed husband.

The instant she saw him she started crying.

One of the undertakers strides up to provide comfort in this somber
moment. Through her tears she explains that she is upset because her
dearest Albert was wearing a black suit, and it was his dying wish to
be buried in a blue suit.

The undertaker apologizes and explains that traditionally, they
always put the bodies in a black suit, but he'd see what he could
arrange. The next day she returned to the undertakers to have one
last moment with Albert before his funeral the following day. When
the undertaker pulls back the curtain, she manages to smile through
her tears as Albert is resplendent in a smart blue suit.

She says to the undertaker "Wonderful, wonderful, but where did you
get that beautiful blue suit?"

"Well, yesterday afternoon after you left, a man about your
husband's size was brought in & he was wearing a blue suit. His wife
explained that she was very upset as he had always wanted to be
buried in a black suit," the undertaker replied.

The wife smiled at the man.

He continued, "After that, it was simply a matter of swapping the
heads."