Those are the ones, Justin. Nashville. Call him and offer him $250 and you will pick them up tomorrow. That is how I snagged my first set of GT40Ps, guy just happened to be selling from an hour and a half north of me, so I saved him the hassle of auction, shipping, etc. Gave him cash and out the door.
This explains the push rod guides I mentioned. Its the easiest give away to tell at a glance if they are hi-po heads or not. http://www.hipomustang.com/images/hipoeng/ You can't see it here, but the HiPo heads have screw-in studs. They did not have guide plates; Ford used "close-tolerance slots" in the head castings to guide the pushrods. This meant they could use ordinary non-hardened pushrods. Screw-in vs. push-in studs was just a matter of machining the casting. http://www.hipomustang.com/images/hipoeng/hipo6.jpg
The std 289 heads (until the switch to rail rockers) also used the slots to guide the pushrods. But the pushrods in these engines were hardened, contrary to what that article says.