Most of the info I have now concerns only Yates C3 heads from the mid 90s and newer. Here's some info on the older stuff (A3/B351/C302/D302 SVO High Port Canted Valve Aluminum Heads) taken from a post by Dan Jones on the Pantera Forum. The link is here:
http://pantera.infopop.cc/eve/forums...2/m/4560012355