This is interesting. I have a 69 Hemi runner I got in January 1970 and I remember the first time I removed the part in question the pin was already stuck. I could not free it and replaced it in the assembly still frozen. I never had brake problems until recently, due to a leaking master cylinder, so this must be a case of 'I'd rather be lucky than good'. I will add that there is some play between the square end of the pin and the corresponding hole in the bracket, and that helps!