With that 2 piece rotor and hub assemblie, that's a design that was used on the 69, 70, 71, 72, single piston calipers.
They ARE NOT 66-69 vintage B body parts.
They to me appear to be "C" body brakes, by looking at the spindle.
That spindle looks to be pretty "tall" to me.

And to answer your other question.
NO, C body brakes don't work on a B body car, or any other body style for that matter.
For one thing the spindle is way too tall.

What car does you buddy say they came off of anyway, or does he even know?

If you want some disc brakes on your car, look for a decent set of 73-76 A body brakes, or 73-74 E body brakes.
Rotors, calipers, are cheap for them, and readily available.
And or, even later.
Aspen, Volare, Diplomat, 5th. Avenue, 73-up B body brakes are good candidates, from donor cars.