There is a "classic brake shop" in LA that had the calipers cast up in aluminum.
I didn't get there fast enough to get a set. Apparently they only tried an initial set of 50 or so and had problems with the foundry casts as porous?
I am also told that Ford did cast some up as SK parts and tested them by passing them out to racers for free to try. That is or was how Ford Engineering worked then. For whatever reason the part was not approved to go further into production.
I can tell you that side by side the 4 piston Ford caliper is VERY similar to the Gurling in many respects but Ford eventually abandoned the design in favor of one large piston that went into production in the '68 model year.
The T-bird 4 piston calipers had the tendency of freezing up one or more of the pistons in daily useage. So the design was probaly one of those 51% problem, 49% no problem parts that looked for a better, and cheaper design for production cars.
It can be pointed out that an aluminum caliper saves unsprung weight but there is little you can do to reduce the added mass of a 12 inch by 1.25" rotor.
In my own useage of both the 67 t-bird calipeer, the 68 Mustang caliper and the Pantera Girling caliper, the Girlings freeze up more then the others do.
The T-bird brakes are a very good solution to more braking in the front with minimal switch over issues. The "issues" being fairly simple to fix even for the do-it-yourself doer. Although not everyone has a mill in the basement to carve out such beautiful adapters like those Dudejack? Very nice.