Alright I think some people are getting confused. He is asking about the exhaust gas passage for the Smog pump system. (themactor system) Any decent machine shop should be able to drill the themactor passage since GT-40P's do not come with the thermactor hole drilled (if the casting itself allows this). The EGR system is different then the Themactor system though both deal with exhuast gas and emission controls. The EGR passges are present in most GT-40P heads (I believe later castings do not have it), if you look in the number 2 and 6 exhaust ports you can see the egr passages which go through the head and into the intake. Both the EGR passages and Thermactor holes can be drilled if the castings allow which I'm sure they will.
I have a question regaurding the EGR passages, what is the best way to fill them? Since I plan on deletling the EGR system and using non-egr intakes I figure fill the passages in the head to, do they hurt flow much? Thanks.