68 Z/28 Engine Smoking - Any Ideas?

[68 RS Z/28]

I have an intermittent problem I can't track down so I thought I'd ask if anyone has any ideas on this. The car is a bone stock 68 Z/28. The engine has about 1,500 miles since a complete rebuild. This work was done by a very reputable local machine shop. The crank was turned .010 over; each cylinder in the block was bored and sleeved to allow re-use of the original pistons; rotating assembly was balanced. New cam that is supposed to match the original profile. The car has the correct original heads with 2.02/1.60 valves, aluminum intake as well as the correct Holley 780cfm carb and dist. Both the carb and dist were redone by Camaro Hi-Performance. The A.I.R. system is functional and on the car. Overall it runs well. No funny noises, lots of power, etc. What it is doing is smoking occasionally, sometimes really badly. This seems to happen only at idle speeds. I had the car out yesterday for the final run of the year. I drove about 20 miles through the country at speeds up to 60mph. I didn't notice any smoke while driving or at stop signs/lights. As I got home and pulled into the garage however she started to smoke. One guy told me that he thought there was a blueish tinge to the smoke, although I'm not so sure about that given the recent rebuild. As I say, its only intermittent. Has me stumped. Any ideas you have would be appreciated. Thanks in advance.