Thanks for mentioning Aus Ford Parts Rick. I've actually been in contact with Lawrence (the Aus Ford Parts guy).
If a Pantera owner wants to lower the powerband of his Pantera's engine, the Australian heads are the small port heads to use because of the extra flange width around the exhaust port. There are two choices in Australian heads, 302C heads with quench chambers or 351C heads with open chambers. There's a 14cc difference in combustion chamber volumes between the two heads.
You can achieve the same results with either head, the paths are slightly different. The 351C heads have open chambers which flow better "off the shelf" (they're worth 10 bhp or more), but require pop-up dome pistons to make equal compression. The 302C heads need some grinder work in the combustion chambers to unshroud the valves (and flow as well as the open chamber heads), but can achieve good compression with a flat top piston even after opening-up the combustion chamber.