Looking for 6-1/4" Midland Brake Booster. 67 to 69 A-Body front disc application.
For size reference, photo of seven inch with measurement has been added.
If you are looking for a factory Midland unit for 67-69, which matches your listing pics, it would be the Midland 7” 1967-1972 application unit.
The second pic you included in your wanted post reflects a 3.5” Radius measurement, which also matches the 7” diameter referenced. Midland does/did not make a 6 1/4” unit installed in 67-69 MOPARS. Booster Steve could confirm this.