Metal Schmetal!
If the block and head aren't perfect the metal won't seal it....
I've experienced the EXACT same problem with a similar amount of prepwork and care and this weekend after pulling my head off the gasket told all...
The gasket looks fine however you can see carbon tracks on a sealing surface to the water holes in the block on cylinder's 2 and 3.
It was dead center between the studs and a retorque with ARP lube made absolutely no difference.
I could have got the head decked and tried again but it's not worth the hassle..
I just bought a core and am going all out on it.