WHILE ON VISUAL APCH TO LAX RWY 24L; B737 CREW ADVISED THEY HAD SAAB TFC IN SIGHT FOR RWY 24R. LNDG SIDE BY WITH THE SAAB; THE CREW NOTICED A SECOND SAAB HOLDING TO CROSS THEIR RWY AND WONDERED IF THEY HAD SPOTTED THE CORRECT ACFT.

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WE WERE ON DOWNWIND FOR RWY 24R AT LAX ARPT APPROX 5000 FT AGL. LAX APCH CTL SAID WE HAD TFC AT 1-2 O'CLOCK; A SAAB; DSNDING FOR RWY 24R AT LAX. WE TOLD LAS APCH THAT WE HAD TFC IN SIGHT; AND WERE TOLD TO FOLLOW THE TFC FOR THE VISUAL RWY 24R. LAX APCH THEN ASKED US TO BEGIN OUR BASE TURN. HAVING THE TFC AHEAD IN SIGHT; WE COMPLIED WITH THE REQUEST. DURING THE TURN; LAX TOLD US TO SWITCH TO RWY 24L AT LAX. THE CAPT ASKED ME TO DIAL IN THE RWY 24L LOC FREQ. (WE HAD THE RWY 24R LOC FREQ AND VOR IN BOTH RADIOS). I DIALED IN THE RWY 24L LOC FREQ FOR THE CAPT; BUT WHEN I LOOKED UP I HAD LOST SIGHT OF THE TFC AHEAD. IMMEDIATELY; WE REALIZED THE RWY 24L LOC FREQ WAS NOT WORKING; UPON WHICH THE CAPT ASKED ME TO REDIAL THE VOR FREQ. SO I REDIALED THE VOR FREQ AND SWITCHED IT TO THE ACTIVE RADIO. UPON LOOKING UP (AFTER SO MUCH HEADS DOWN TIME) I HAD LOST SIGHT OF THE ARPT AND THE TFC AHEAD. I TOLD THE CAPT ALOUD THAT I DIDN'T SEE THE ARPT OR THE TFC. HE SAID HE HAD THE TFC IN SIGHT. WE CONTINUED OUR R TURN TOWARD THE ARPT. ALMOST AS I GOT THE VOR FREQ DIALED IN; THE CAPT SAID 'I HAVE THE ARPT;' AND I AGREED. AS WE CONTINUED THE TURN TOWARD RWY 24L; WITH AN ACFT AHEAD IN SIGHT; THE CAPT SAID 'WE HAVE TFC OVER THERE' (POINTED TO 1 O'CLOCK POS). I IMMEDIATELY SAW THE ACFT. I LOOKED AT THE TCASII AND IT SHOWED THE TARGET APPROX 1/2 MI; 1000 FT BELOW US. WE SEEMED TO BE ON PARALLEL COURSES. LAX APCH TOLD US TO CONTACT LAX TWR. I CONTACTED LAX TWR AND TOLD THEM WE HAD THE TFC IN SIGHT. HE SAID WE WERE CLRED TO LAND RWY 24L. JUST TO CONFIRM I ASKED 'DID YOU CLR US TO LAND RWY 24L?' LAX TWR CONFIRMED 'YOU ARE CLRED TO LAND RWY 24L;' FOLLOWED CLOSELY BY A REQUEST TO THE SAAB LNDG ON RWY 24R TO SLOW TO MINIMUM APCH SPD. WE PASSED THE SAAB ON A 1/2 - 1 MI FINAL. THE LNDG AND TAXI IN WERE NORMAL. HOWEVER; WHILE TAXIING IN; WE NOTICED A SAAB AND JET STREAM THAT LANDED BEFORE US HOLDING ON THE TXWY. SEEING THESE ACFT GOT THE CAPT AND ME WONDERING IF WE REALLY HAD BEEN FOLLOWING THE ACFT THAT APCH CTL HAD INTENDED. CONTRIBUTING FACTORS: 1) ATIS WAS CALLING 7 MI VISIBILITY. IN THE AFTERNOON HAZE IN LAX; INFLT VISIBILITY WAS PROBABLY 3-4 MI. 2) ASKED TO DO A VISUAL FOLLOWING A SMALL COMMUTER PLANE OF WHICH THERE WERE SEVERAL IN THE LCL AREA. 3) ORIGINALLY PLANNED VISUAL TO RWY 24R CHANGING TO RWY 24L CAUSED HEADS DOWN TIME TO CHANGE NAV RADIOS. (HAD TO CHANGE FROM RWY 24R LOC FREQ TO RWY 24L LOC FREQ TO VOR FREQ BECAUSE RWY 24L LOC WASN'T TURNED ON. 4) NOT HAVING A CLR VISUAL ON ARPT. SOLELY FOLLOWING ACFT AHEAD.