Disc brake identification

It’s a slider set up, so it could be either one. Probably the biggest thing to be concerned about is the piston diameter, which you can measure. A-body single piston sliders used a piston that was 2.6” in diameter from ‘73 through ‘75, everything else used a 2.75” piston (including the ‘76 A’s). The larger piston gives you more braking force.

Some B-bodies used the pin style calipers depending on the year, so if you’re buying parts you’d want to make sure they’re for slider calipers. As long as they’re 2.75” pistons I wouldn’t worry about it too much, unless you’re trying to match up casting dates or something.