continuing to have brake issues Help

[Ken 6645]

when I bought my 64 bird I knew that the brakes were needing rebuilt The pedal
was just as hard as a rock...SO I replaced the brake hoses ,wheel cyls,hardware, brake shoes, power brake booster,master cylinders...Brake petal still as hard as a rock...After driving it around the house about 6/8 times it suddenly had a good fair petal .next day the brakes went from good brakes to no brakes without any warning..Is there a vacuum canister that I can't find? HELP ...I'm stuck
I didn't replace because the lines were new and worked fine when bleeding the brakes.It wouldn't be a bad master cylinder,would it??
thanks in advance for your help
Ken 6645