Classic/Antique Car Repair: 1962 impala, chevy engine, new spark

Question
I install a 305 chevy engine into a 1962 impala.  The engine runs finewhen it is idling but when i put it in drive it starts to stall or some times it stops.  I install a edolbrock intake and a edolbrock carb  (500cfm).  I also have a spacer.  It turns on fast.  The problem is just lack of power and stalling when it is in drive.  it has new spark plugs and wires. i tried adjusting the carb but the same thing.  Timing is good.  I also installed a new cam.  I was just one step from oem.  It is a duration of 260°/260° The engine ran strong in my other car.  

Answer
 Hea
     Jose;
          You say you put in a new CAM did you adj. the valves right ? also if you put in a cam you put the distributor back in if it is off buy one (1) tooth it can cause all kinds of problems. also do you have a VACUME leak any place or does the carb. have a vacume feed or a line that should be used or / not used ? Start from the distributor and check that it is in right. than check the valves , what are they set at ? hyd. or solids ?it might just be a vacume problem.
 OK
      GOOD LUCK
Roger