[cyclone427428]

I got my Galaxie today and I looked at the casting number on the heads and it's C3AE-C. It's a Z code 390 car with a 4 barrel. When I search on these heads it most often comes up as 406 heads with 2.03 In. and 1.65Ex. I have come across information as high altitude 390s getting these heads with the standard 2.03In. and 1.55Ex. Is there such a thing as the two different heads with the same casting number? In my how to rebuild bb FE book by Steve Christ these heads are listed as high performance 406 heads. Anyone have any info on if there are two different heads with the same casting number? Thanks. Rob.