so it is a straight through, but to this bracket you see at the back of the booster.
it adapts the booster to the firewall manual brake holes.
they both have different bolt patterns.
the bracket has the weird pivot linkages in it.
I was hoping to find a booster that bolted to the bracket.
the intrepid booster was closest, that it has the correct bolt pattern to the bracket. But the tail shaft out wasn't quite right.
boosters have 4 mounting studs that make a 3.375" square center to center on the studs.
There isn't much room deep though for it to mount to the bracket for the push rod.
I remember having to cut a couple inches off the stud in the back so it would fit the bracket and bolt on.