B737-300 CREW EXPRESSED CONCERN ABOUT WAKE TURB FOLLOWING A B747 IN IMC FOR RWY 24R IN LAX CLASS B AIRSPACE.

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THE FLT WAS ARRIVING IN LAX. THE WX WAS OVCST AT THE ARPT; BUT VMC ON FINAL. THE CTLR SLOWED US TO 170 KTS AND ANNOUNCED WE WOULD BE FOLLOWING A B747. WE HAD THE TFC POINTED OUT TO US AS HE TURNED FROM DOWNWIND TO FINAL IN FRONT OF US. APCH GAVE US A SPD REDUCTION TO 150 KTS WHILE STILL ON A LONG FINAL (APPROX 16 MI). REALIZING THE B747 WAS CONFIGURED AND SLOW; I WAS CONCERNED THAT HE WOULD BE PRODUCING A STRONG JET WASH. IF I'M SLOW; I WOULD BE AT A LESS THAN IDEAL SPD TO COUNTER HIS VORTICES SINCE I WOULD BE CONFIGURED. I REQUESTED S-TURNS TO THE N FOR SPACING INSTEAD OF THE SPD ADJUSTMENT; WHICH WAS DENIED. THE CTLR'S OPTIONS WERE TO SLOW OR RECEIVE A BREAKOUT AND RESEQUENCE. I CONSIDERED FLYING HIGH ON THE ILS GS; BUT SINCE THERE WAS A 10 KT TAILWIND; I WAS CONCERNED I'D HAVE TO 'UNSPOOL' ON SHORT FINAL AS I BROKE OUT OF THE OVCST. I DID NOT WANT TO BE SLOW; LOW; UNSPOOLED AND THEN ENCOUNTER JET WASH. I AM UNCOMFORTABLE BEING PLACED BEHIND A HVY WITH MINIMUM REQUIRED SPACING AND HAVING THE CTLRS USING MINIMUM SPDS TO EFFECT THIS REQUIRED DISTANCE. THE REQUIRED STATEMENT ISSUED BY ATC TO 'USE CAUTION; FOLLOWING A HVY' SEEMS A BIT USELESS AND INEFFECTIVE WHEN IT WOULD APPEAR MY ONLY OPTION AT THIS POINT WAS A 'BREAKOUT.' I WOULD CONSIDER 5 MI BEHIND A HVY ADEQUATE AS LONG AS I CAN MAINTAIN 170 KTS.