master cylinder question

i seem to be really lost :/ thought i knew the answer but now i dont know lol i just switched my drum/drum to disc/ drum. my 72 duster come with manual drum brakes. although when i went to orilys to get a manual master cylinder they could only find them saying that their for power brakes and they didnt knw if i could just bolt that on and use it that way. also the doorman one says its for power brakes. is there any difference between the two? i really dont knw if i can just buy the power one bolt it on bleed the brakes and be good very lost sry i sound dumb.