I don't have access to a flow bench, but it looks like the slant six head could really use the port entries(int) and exits(exh)'raised'. How much can you 'raise' these before you strike air?

fglmopar@aol.com

There is about .400 of material to work with at the port enterance, there is more thickness along the floor of the runners so look to grinding some material off the middle of the port floor to help straighten-out some of the curve.

The trouble with sand castings in general is that they have a lot of part to part varation, all the cores are "hand installed" and the sand molds were made from many different core boxes and patterns in use over the years. The best you can do is section-up a junk head of the same appx. year / p/n and use that as your guide to where the thin sections are, even this is not a "for sure" road map but it's less expensive then sonic or x-ray checking each area.
DD