i have a1993 f150 xlt shortbed can it be extended

YES! sell the truck and buy a 8 foot bed truck, this is the easiest, cheapest and smartest way to go. If the truck is in good shape you might want to trade it for a 8ft bed truck, The trouble you will need to go to leighten the frame and get a new bed, plue the suspension upgrades, and a bunch of other stuff. I would recommend getting a new truck. Hope this helps, best of luck.

agreed

Agreed, get rid of the shortbed and get a regular bed. I know for example that my '07 Dodge Ram 1500 is the LWB (long wheelbase) model with the 8ft. bed, the crew cabs and others running around are a shorter wheelbase. Too much work required beyond just dropping a bed on and done.