Check out this guy call Lars Grimsrud. I have used his articles to tune my 327 with vortec heads and Proform HEI. I replaced the adjustable vac can with a stock vac can he listed (AR31 $9 Auto Zone) and it has tuned my motor very well.
http://www.corvetteclub.org.uk/files...and_timing.pdf
http://www.nastyz28.com/~ericf/tech/vacadvance.pdf