"Scrounging" is not a "Pontiac thing". Parts are available at every engine parts warehouse, just like Chevy. Yes, they DO cost a bit more, but they are NOT hard to find. 326 pistons can be an adventure...(:-
Considering the Firebird 400 and T/A had ALL the small block Camaros "covered with a blanket", I really don't see Pontiac's marketing people worried AT ALL about Camaro in '69. Pontiac was #3, far "ahead" of where they were at any time in recent memory. If they really wanted a slice of the "Camaro pie", I think they would have flooded the market with T/As instead of severely limiting them. I think the 350HO cars were just a "bone" thrown to more economically-minded Pontiac buyers. With the exceptin of GTO in that era, for the most part, Pontiac wasn't trying to outsell Chevy. They didn't NEED to "try" with GTO until 1970, when GTO sales took a dive (strange, too, as the '70 is among the finest of all muscle cars) and SS FINALLY swept "up".
In some ways, "48" is considered the "second best" D-port head. 12 takes "top honors" ('70 350HP-366HP 400s). 12 has about the same intake flow as 670 and 48 (210 @ .500, untouched). The exhaust, however, goes an additional 25 CFM over ALL the other D-ports, at just over 175 @ .500. Some 48s were also machined with an "odd" chamber, similar in shape to the Ram Air IV heads ("compact wedge"). I've only seen a few, and those on KNOWN Ram Air III (simply called "Ram Air" in '69) 366HP 400s. 48s are getting VERY rare these days, and is NOT a good head for a 455 unless drastic steps are taken to reduce compression (12:1 with a flat top), OR it's a dedicated "race" engine, using only 100-plus octane race gas. Without porting, a 455 will "run out of breath" with these heads before 5,500 RPM. Once ported, a d-port is a d-port is a d-port...