Okay, what is this thing on my bail?

Okay, what is this thing on my bail?

Thanks guys. Lets update the code info on the part number and tag cheat sheet:

Years___Application_____________p/n_______Bore
1966... Fixed Ft calipers, Manual.....................1"
1966... Fixed Ft calipers, Power......................1"
67-70.. Fixed Ft calipers..............280 8600.....1"
71-72.. Fixed Ft calipers..............346 1178.....1 1/32
73-74.. Floating caliper, Manual...358 0146.....1 1/32
73-74.. Floating caliper, Power.....358 0112........15/16
1975.. Floating caliper, Power......____0357

townsend said
The 1976 model is different from earlier models.
The master cylinder, calipers and proportioning valve were changed in 76. The caliper pistons increased in size which probably required a new master cylinder and proportioning valve.
...

1976?......................................____0236..........15/16
IIRC this tag p/n comes from here
https://board.moparts.org/ubbthread...ntthread/Board/1/main/187113/type/thread.html