After just spending 40 minutes digging through the factory service manual I'm gonna retract that statement.... It appears in 68 some cars got self adjusting brakes & some didn't.. No explanation of what did or did not get them... Currently I own a 68 Coronet R/T that came with four wheel 11" drums & no self adjusters... When I get done building it it will have self adjusters on the rear... And discs up front....
In the past I owned a 68 Charger R/T also with four wheel 11" drums.. No self adjusters...
We all know what is being created in the photo below right? Elephino
OP has a '66, but that doesn't matter I don't think...
The whole self-adjuster vs. none thing is indeed sort of confusing to me, after doing way too much research on it.
My own experiences with b-bodies almost exclusively over the decades is much like yours in this case, as I never
owned one with self-adjusters on it (and some were still outfitted with factory brakes when I bought 'em).
That said...
I checked out the FSM for 1966 (thought I'd had enough of researching Mopar drum brakes the last couple years...
).
According to that particular FSM, from what I can tell self-adjusters were in use
except for "heavy duty and police".
The FSM shows the typical Bendix self-adjuster setup on all sizes OR the heavy spring passing over the star wheel,
as Fran and others have shown.
*sigh*
I wound up adding self-adjusters to the rears - and leaving them off the fronts, after a lot of trial and error.
The car just works better that way. I won't pretend to understand why.