MAYBE: I know a 76 chebby works but I'm not sure 'bout 77s. Have your local store look up the P/Ns for the spindles for 76 & 77. If they're the same, all is good.
REMEMBER: They have to be from a 1/2 ton chebby. A 3/4 ton wont work. And be sure to get the rubber brake line thats attached to the calipers, or at the very least make sure the banjo bolts are there.
ALSO: You will need the hub/rotors for a 76~86 Bronco ($35. per?) unless you want to run six lug wheels in the front only.
SUMMARY: If they're the right parts, it will work. :
Thats a great price too. Even if the calipers are trash and need to be replaced you'll end up spending less than half of price of a kit.