1973 Impala Oil Leak!!

I have a 73 Impala that smokes only when i'm driving at high speeds (70-80 mph). I can drive in the city all day without any problems or any signs of a oil leak but when i get on the interstate and drive at high speeds, my car will smoke. the smoke is coming from the driver side.  the driver side manifold will get wet with oil.  Right above the #7 spark plug on the corner of the manifold will but wet.  also, my plug wires will have fresh oil spots on them after i drive at high speeds.  I checked the valve covers, dip stick tube, and oil filter. I have had it checked by different mechanics and no one can seem to find the leak.  the dip stick tube had a small leak but I dont think it was causing the manifold to get wet. I have no idea where the oil is coming from. Any suggestions???? Please help.  

Make sure the PCV system is working properly. Without it, crankcase pressures could be pushing oil out at high RPM.  
Jim
70 El Camino
461 solid, m20,
pics in readers rides

what should i check for?  I'm not too familiar with the pcv system  

i REPLACED THE PCV VALVE.  THE ONE THAT WAS ON THERE WAS FOR A 1977 IMPALA.  WOULD THAT MAKE A DIFFERENCE EVEN THOUGH THEY BOTH HAVE 350 ENGINES  

It could. The little check valve in PCV valves can vary depending on application, so it makes sense the wrong application PCV valve could be the cause of your problem.  

Also check the oil return holes it the head  

do you think it could be the oil pressure switch?  

No, that will only have an affect on the gauge/light. If the PCV system is working properly, high crankcase pressures are usually the result of blow by. This is usually caused by compression getting past the rings or valve guides. Slow oil return, as mentioned above, could also be an issue.  
Jim
70 El Camino
461 solid, m20,
pics in readers rides

what's a solution to the problem if it's high crankcase pressures?  

If it's blow by you will probably need to replace your rings.  You should do a compression test on each hole and see where you stand.