disc brake pre72/post73 proportioning valves

Thanks for all the comments. I would like to repeat what I think has been said to verify. I can use any disc/drum proportioning valve from a 67-76 a-body to use on a sbp K/H front disc and 9"drum brake system. If I changed to 10" or 11" rear drum brakes, I would not need to change the proportioning valve as they are all the same. Would this be correct? Also, to verify, the drum/drum a-body valve would be used if I went to disc brakes front and rear? Thanks again, dan...