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1) Get a double ended stud and drill/tap out the hydroboost mounting flange to receive a Helicoil adapter and tightening nut on the back side of that mounting flange, and then just use the proper nut on the extended stud as you would have with the original bolts.
2) Get a junkyard hydroboost unit and scavenge the bolts from it.
3) Call Power Brake X-change ( Power Brake X-Change Inc. ). They rebuild brakes and may have a source for bolts, or know of someone else who does. The guy who used to be the "expert" there is Harold, but the reference I've seen recommending him is now 12 years old and he may not be there any more (https://www.ford-trucks.com/forums/3...ts-needed.html).
4) Replace the hydroboost with a new unit. If you have high mileage (>200K), and it's the original unit, it's more money, but it's approaching the end of it's life anyway. Mine went out at 286K miles.
There used to be a company called King Bearing that carried just about any size/configuration of bearing that you could think of.
Perhaps there is a similar source for hardware like this but IDK.
So I solved my challenge, it's probably not a method I'd recommend so I'd rather not go into details . Suffice to say, I now just need to rebleed the brakes cos I didn't get all the air first time and she grabs one front calliper before the other if you go hard on the brakes.