i have a pair of GT40P heads for sale.
looking for $350
the heads have NEVER been used. they were assembled and checked over by Alan at Folks machine in Norman. stainless valves. i can probably get more specific on specs if requested.
i was going to use them on my 289 but i went with a 351w instead and no one makes headers for a 64 1/2 mustang with a 351w and gt40p heads.
for pics check here. ....