THE NORMAL FUEL LOAD FOR THE FLT WAS 1500 LBS, BUT WITH A FORECAST TAIL WIND & AN ESTIMATED FLT TIME FOR ONLY 1+10, THE CREW ACCEPTED THE LOWER INDCTD (950 LB) FUEL LOAD. THE FLT WAS UNEVENTFUL UNTIL AN INDCTN OF 250 LBS PER SIDE, THEN THE FUEL 'SEEMED TO DISSIPATE FASTER.' WITH AN INDCTN OF 150 LBS ON DWNWND, THE COPLT RCMDD DECLARING AN EMERGENCY. THE CAPT'S RESPONSE WAS TO ASK ATC FOR THE ANTICIPATED LENGTH OF THE DWNWND LEG. HE WAS TOLD 20 MI. PRIORITY HNDLG WAS REQUESTED, BUT WAS ONLY AVAILABLE FOR A DECLARED EMERGENCY. THE APCH WAS CONTD WITH NORMAL HNDLG FOR APRX 10 MIN. AT 1608:39, THE CREW DECLARED AN EMERGENCY, THEN RPRTD THE ACFT WAS OUT OF FUEL. IT CRASH LANDED ON ROUGH TERRAIN, SHORT OF RWY 8. AN EXAM REVEALED FUEL SENSORS HAD BEEN IMPROPERLY INSTALLED (INTERCHANGED BTN THE INBRD & OUTBRD TANKS). THUS THE GAGES INDCTD ABOUT 180 LBS MORE THAN THE APRX 763 LBS THAT WAS ACTUALLY ABOARD AT TKOF. A SPCL 500 HR INSPN OF THE ENTIRE FUEL SYS WAS MADE ON 7/8/84 USING THE 'WET' METHOD, BUT ONLY THE CAPACITANCE METHOD CHECKS EACH INDIVIDUAL SENSOR