CPR LTT TKOF OVERWEIGHT FOR RWY AVAILABLE.

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WE'VE BEEN INTO THIS ARPT A HUNDRED TIMES...BUT THIS TIME COMING OUT WITH 7 PAX (MORE THAN USUAL LOAD). UPON 1ST LNDG; RWY WAS DISPLACED 500' ON NE END (AS PER NOTAM) BY SECURITY VEHICLE PARKED ON END WITH FLASHING LIGHT...THEN GND CTL CLRED US FOR TAXI FOR TKOF TO ALTERNATE 4008' RWY. I KNEW THAT WASN'T ENOUGH RWY SO I ASKED FOR THE SAME NE RWY THAT I LANDED ON (WITH DISPLACED THRESHOLD LEAVING 4500'). THERE WAS SOME MISUNDERSTANDING OR ASSUMPTION ON MY PART WITH GND CTL ON WHICH RWY DEP OF 4500' NE RWY (REASON WAS BECAUSE I KNEW IF I TOOK OFF FROM NE [ON SW (HEADING) I WOULD BLAST CONSTRUCTION WORKERS; SO I WAS REQUESTING OTHER DIRECTION FOR TKOF). GND CTL GAVE ME SW DEP FROM INTERSECTION M (AGAIN I ASSUMED THIS TO BE THE 4500' DISPLACED THRESHOLD POINT!) WITH TEMPERATURE BEING HIGHER THAN I PREVIOUSLY FIGURED FOR TKOF; I ELECTED FOR 2ND SET OF FLAPS (20 DEG). UPON ROTATION (JUST AT END OF RWY) I KNEW SOMETHING WAS WRONG. I UPON TALKING WITH NEW COPLT LATER SHOWED ME THAT THE INTERSECTION I ASSUMED TO BE THE 4500' DISPLACED THRESHOLD POINT WAS ACTUALLY ONLY 3726'. (SAME LENGTH AS PARALLEL RWY)!1 COPLT NOT BEING FAMILIAR WITH THIS ACFT'S TKOF PERFORMANCE. DIDN'T QUESTION MY NOT BACK-TAXIING FOR TOTAL USABLE 4500'. LOOKING BACK ITS EASY TO BLAME THINGS LIKE NOT HAVING A DISPLACED THRESHOLD MARKING PAINTED ON RWY DURING DURATION OF NEW CONSTRUCTION AND COPLT NOT CONFIRMING THE INTERSECTION TKOF LENGTH REMAINING AND SO FORTH BUT IN REALITY IT WAS MY ASSUMING AND COMPLACENCY AND RELIABILITY OF ACFT THAT COULD HAVE BEEN A REAL MESS (ACCIDENT WAITING TO HAPPEN). BY THE WAY THE TKOF PERFORMANCE CHARTS SHOWED US 2000 LBS OVER GROSS FOR 3726!! REAL STUPID! BUT NOT AGAIN.