Blue Smoke From Exhaust

I have a 68 Dart with a newly rebuilt 72 340. I have noticed blue smoke coming from the exhaust when I get on it and when I lift. I checked my plugs and there is oil in the threads and on the washer. The smoke does seem to come and go. I'll notice it while idling at a one red light but not at the next. The car runs really strong. The engine has 10.5 to 1 pistons, 2.02 valves, air gap, 650 carb, headers, etc... Am I hurting anything running it? Should I park it? I am a beginner, this is my first project. Her are some pics of the plugs.IMG_1160.jpg IMG_1161.jpg IMG_1162.jpg