Yes, the clutch safety switch is up under the dash. Should be screwed to the left side of the pedal hanger bracket if I remember correctly.
Looks like this:
http://www.ebay.com/itm/1970-1978-GM...53fe15&vxp=mtr
I don't know if that is the
exact switch your truck takes (the ebay listing is showing it for cars) but the truck one is similar looking.