FLT CREW; FLYING AN MD90; TRANSPOSES ASSIGNED HEADING INFO FOR ALT ASSIGNMENT. ARTCC CTLR INTERVENES TO REASSIGN INTERIM ALT. FLC DISTR WITH AIRBORNE RTE CLRNC AND SAME NUMBER USAGE; BUT DIFFERENT APPLICATION.

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FLT PLAN FILED: LGB..FIM.J1.AVE.PNX2.OAK. CLRNC RECEIVED RADAR VECTORS..LAX..GMN-AVE AS FILED. LAX DEP CLRED US FROM 9000 FT TO FL230 DIRECT GMN. THEN CLRED FL310 (AND/OR HDG 310 DEGS) AFTER GORMAN. WE QUESTIONED FL310? IT WAS CONFIRMED FL310 AND WE STARTED CLB. IN THE MIDST OF THIS; WE CHANGED TO ZLA AND TOLD GMN..BSR..SAUSALITO (OAKLAND LNDG SE). OVER GMN WE STARTED TURN TOWARD BSR AND CONTINUED CLB. CTR ASKED 'ACFT X; WHERE ARE YOU GOING? ARE YOU ON A 310 DEG HDG?' WE REPLIED DIRECT BSR; BUT WE WERE TURNING TO 310 DEG HDG NOW. HE REPLIED; 'STOP YOUR CLB.' WE DID. HE LATER CLRED US TO FL310. THERE WAS CONFUSION WITH SIMILAR ALTS AND HEADINGS; FL310 VERSUS 310 DEGS AND A ROUTING CHANGE. THE OTHER PLT HAS DONE MOST OF HIS FLYING ON EAST COAST AND WAS NOT AS FAMILIAR WITH WEST COAST LOCATIONS. WE SHOULD HAVE BEEN MORE ASSERTIVE IN CONFIRMING 'HEADING' VERSUS 'ALT' AND ALSO MORE ALERT TO 'DID WE HEAR THE CLRNC' VERSUS 'DID WE THINK WE HEARD THE CLRNC?' SUPPLEMENTAL INFO FROM ACN 397320: WE WERE ENRTE AND CLBING AS FILED. CTR TOLD US TO STOP CLB AT FL260. A QUESTION AROSE AS TO FL310 OR HDG 310 DEGS. WITHIN 3 MINS OF THIS OCCURRENCE WE WERE CLRED TO CLB FL310.