Originally Posted by Cloaked
You can find them here (maybe) http://www.tristatecylinderhead.com/
A friend of mine snagged a set a few months ago for US$575 + shipping. Their site showed plenty in stock (at that time) but when he called, they had none in stock but took a core and built him a set in three days. Upon his request (recommended) they drilled the bolt holes out to 1/2" dia. You'll have to reuse your current push rods and rocker arms but the rest is plug and play.
I'm sure this has been covered, but why do you have to drill out the bolt holes to 1/2"?
Do the GT40 heads come with smaller bolt holes than the what 351 heads have?
Just trying to catch up!