Head

Doug Dutra on modifying the combustion chamber:

http://www.slantsix.org/articles/combustion-chamber/sl6-combustion-chamber.htm

Doug Dutra article on porting the Slant 6 head:

http://www.slantsix.org/forum/viewtopic.php?t=41693

This post has a chart showing flow-bench numbers for the head with 9 steps from stock to fully ported:

http://speedtalk.com/forum/viewtopic.php?f=1&t=22094

as mentioned in the 'too bad you're so far' reply, shave the head and go to 1.70/1.44 valves