vw aircooled engine smoking?

So, my buddy and I have built a 1776. We have quite a bit of experience with old VWs and have never had this much trouble with a new build.

New piston/ring/cylinder set, rebuilt heads.

1st time we fired it up, it started smoking. We shrugged and took it for a spin, but it only started to smoke more. We decided to pull it and tear it down. #4 cylinder has some carbon buildup on top of the piston, we thought maybe we just installed the rings incorrectly - so we pulled all 4 and did them again. 2nd time we fired it, it still smoked. So we decided to try a used set of heads from a good running used engine.. We're still getting white smoke at high RPM or especially after revving it up.

The only things we can think of are that:

a) the cylinder, rings, or pistons are defective. They are used and not returnable.

b) the rebuilt heads were not right. AND the used heads we thought were good aren't.

or

c) the rings just aren't seating properly. We assembled it with synthetic oil, since it's what we had around.

anyone?