To remove the tank, begin by disconnecting the wiring and vent line, & removing most of the skid plate bolts. Most Broncos use bolts with a 10mm head & 13mm nut. Most '80-96 pickups use only straps, with a 13mm nut on TOP of the crossmember.
For more info, see this album:
http://www.supermotors.net/registry/2742/33276 
