SINGLE PLT HAS AN NMAC WITH ANOTHER ACFT WHILE UNDER FLT FOLLOWING.

Narrative

MY ACFT WAS BTWN 12500 FT AND 12700 FT IN GOOD VFR BTWN CUMULUS BUILD-UPS; AND ABOVE THE UNDERCAST BY 1000 FT VARIABLE. I WAS CLBING TO 14500 FT TO REMAIN VFR AND IN CONSTANT COM WITH THE CTLR -- HAVING INFORMED HIM THAT I WAS DEVIATING ON MY ALT AND HDG -- AVERAGE HDG 290 DEGS TO AVE (AVENAL). WITHIN THE EVENT TIME FRAME I WAS INFORMED OF 2 TARGETS -- ONE A COMMERCIAL AIRLINER WHICH WAS IN SIGHT; XING FROM E TO W; 2-3 MI IN FRONT. THE SECOND TARGET; A CESSNA 210 RPTED AT 1:30 O'CLOCK POS; 13000 FT AND NOT IN SIGHT. THIS TARGET MUST HAVE BEEN IN OR BEHIND CLOUD AND POINTED AT ME. THE NEXT RPT BY THE CTLR (WHO WAS IN COM WITH BOTH ACFT); WAS THAT THE CESSNA WAS AT MY ALT 12700 FT ABOUT 11-12 O'CLOCK POS. THIS ACFT PASSED BEHIND AT ABOUT 400 FT AND 50 FT HIGH. THE C210 WAS CLRLY OBSCURED BY CLOUD AND CLOSING ON ME. IF HE WAS UNDER IFR PLAN HE SHOULD HAVE BEEN HELD AT 13000 FT OR VECTORED AWAY OR I SHOULD HAVE BEEN VECTORED OR ALLOWED TO CONTINUE CLBING TO AVOID POTENTIAL 'CONFLICT.' THE CTLR WAS IN GOOD COM WITH BOTH ACFT BUT ALSO CONCERNED WITH OTHER COMMERCIAL TFC ENTERING THE LA AREA VIA THE LHS AND GMN AVENUES. THERE SEEMED TO HAVE BEEN PLENTY OF TIME FROM THE 'INITIAL' INDICATION OF A CONFLICT FOR THE CTLR TO DEVIATE EITHER ACFT TO AVOID THIS INCIDENT. HE KNEW NEITHER PLT COULD SEE THE OTHER ACFT. IN THE SAME 5 OR 6 MINS I HAD DESCRIBED TO HIM MY GOOD VISUAL CONDITIONS -- HAVING EASILY SEEN THE COMMERCIAL JET THAT WAS POINTED OUT. I HAD NO CONSTRAINTS BY CLOUDS TO STOP ME FROM BEING VECTORED AWAY; UNDER VFR CONDITIONS.