idle problem with long duration cam

Hi, I have a 68 Barracuda with 340. Built years ago with a 305 duration magnum cam. It will only idle at 950 rpm or more in gear. It has a 3500 stall convertor 4.56 gears. I have played with different carbs and done the little air tricks but still wont idle below 950. The car runs good low 12s in the quarter. But I would like a more drivable car that still has the same performance. I still wonder if it needs more convertor as it does seem to pull done in gear. Engine is out I have thought of a new cam. Any Ideas Thanks