Power brake booster bracket - bolt specs?

[bigmuddy]

Now that’s interesting! So by “conical”‘I’m assuming that does mean that it’s “tapered” as I suspected? Thanks for the in depth input and pics!

Hate to be a sayer of nay but I just added an aftermarket booster bracket and had to use standard 3/8x16 bolts. They will work but I think it may depend on how accommodating the threads are on the either the brake bracket and or the bolt you are using.