I just installed a Sun tach on my '68 Camaro, works great, although at idle the needle wavers up and down by about 50rpm at idle...this is a newly built 383 stroker engine, manual trans, 750 Edelbrock carb, Edelbrock intake. Is this most commonly a carb adjustment problem, timing, or other problem?

could be but i think a vacum leak might be the cause.

put a vacum gage on it and see if it fluctuates
make sure you use a vacum port below the carb butterflies.

Hmm, you might be right, I'll go out to the garage & inspect the vacum lines right now...

could be a leak at the intake manifold aswell.

special attention should be taken at the ends of the manifold. (front and back)
those areas are leak prone areas.