When I first discovered "Scarebird" about 20 years ago, I thought it was pretty neat to use auto supply sources rather than salvage yard sources. Cleaner and easier, I suspected. Plus some sort of parts warranty with the supplier/auto supply.
But as things progressed, some of those auto supply parts went into NeverNeverLand/unobtainium. Then alternative parts were noted, which also went there, too, as all auto supply sources can tend to go, just as the OEM new parts go their sooner.
Which then opens things up for the kits from Wilwood, Leeds, and such. Wave the $$$$ and things happen on the porch "to your door". For those who might desire such, but even those kits can, as mentioned, have some issues in fitment or needing other parts (in this case, probably wheels to clear the calipers, or the caliper mounting brackets, much less the needed booster) to make things work.
Chevy did have some 14" disc brake wheels in the '67 or so timeframe, for non-Z/28 Camaros and such. The difference was in how the backside of the wheel was angled/shaped to clear the brake calipers. A 15" wheel would clear, but the drum brake 14" wheels would not. Which is also probably why Chrysler just used 15" wheels only on their power disc brake cars (which meant C-body and Imperials). With 15" wheels becoming standard in 1969.
People in this forum and others have universally mentioned "Booster Dewey" to rebuild power brake booster cores sent to him. All with great reviews.
But then,
@TxDon (1967 Monaco station wagon) and others in the FBBO forum have found a supplier for drum brake linings that could well get very close to disc brake performance without changing anything other than the brake shoes. GTXs and such had 11" brakes, too, just only in 11x3 and 11x2.5 shoe widths (which might not cover older C-body cars, in all cases, unless they came with those sizes). A bit pricey at $198.00 per axle set.
www.musclecarbrakes.com
Funny thing in one of the Hagerty newsletters/magazines was a list of 10 things people always said to do to an older car. ONE was "Got to put disc brakes on it". I smiled, because I experienced (as others in here probably did, back then) that the power drum brakes had enough guts to lock-up all 4 wheels, making the stopping distance more or a contest with the frictional relationship between the tires and the road surface . . . for one stop. But then, too, power discs were know to have much better fade resistance in high-speed stops (like at the end of the drag strip, where the return road suddenly appeared while you were still "at speed".
Just some observations and thoughts,
CBODY67