About 5 months ago I looked into brake boosters. This is what I found: there were no new ones in the US and they cost $900. The rebuild kit is about $200 and also not easy to find.
I've tried 5 rebuilt units from A1 Cardone (about $200+core) and none would hold their vacuum overnight. This is with new hoses and a new valve. They all worked fine as boosters, but when a rebuilt unit doesn't work any better than my 21-year-old one, I send back the rebuilt one.
They're crimped shut, but that's not a big deal.
This document surely will come in useful.
I'm certain that baking the unit at 400F would kill it.
If you need a new one, I suggest heading to the pick-n-pull with a Mity Vac. Get one that holds over 20in and you'll be fine.
Asterix