check out the injector cutout.. (ignore the stuff going on up near the throat, that's where I've been hacking at it)
now compare it with a GM head - notice the cutout is a whole lot smaller, and shorter.
I've never actually seen any internal casting differences (and I've seen a lot of heads!) - until now.
the plot thickens too..
it's a GM head with two nobbly bits on - no grub screws covering the line bore hole either - other GM heads are missing these two bits, and have grub screws sealing off the line bores.