Found it!  Thanks Hoosier, I would not have known to look on the cluster.

   James Q

James:

On a '57, the flasher is attached to the back side of the instrument cluster, I would think '58 would be the same.  It is secured by a springy clip, just slips into the clip.  The flasher may be rectangular in shape so it is not quickly recognized.  Round flashers will also fit into that same clip.  Don't confuse it with the instrument voltage regulator.  It is fastened to the cluster by a single screw.

John - "The Hoosier Hurricane"

I am trying to locate the flasher on my 58 Ranchero.  My service manual says there is no fuse box(!), and the flasher should be in the wiring between the column and the light switch. I cannot find it. Any help would be appreciated!

   James Q