George
I work in a machine shop and if you have the heads I am thinking of, there is no surface cast under the head to close off a water port if it were to be drilled in the correct location. You may be able to heil-arc some aluminum and form the passage walls you need, but this would come at a high price and be iffy at best. The drilling of the heads that 64 Fleetside is refering to may be for the intake bolt pattern on the iron vortec heads from 96-02. That is something circle track guys do quite often. I did my vortec heads this way and I would not recommend doing it. The end holes in all four corners break into the water jacket and are difficult to keep from seeping. Hope this helps
Sean
