Military Vehicle Repair: 1986 m1009 Master Cylinder, master brake cylinder, power brakes

Question
I am wondering what the unit is between the master brake cylinder and the firewall? Power steering hoses(?) go to it and it's leaking inside the cab. Is this thing on all Blazers or just military. Is there an O ring that can maybe be replaced where the actuator shaft from the brake pedal goes in to it?

Also, any idea where I could get the black out lights? All mine were gone when I bought it.

I appreciate any help.

Answer
That thing is a Hydroboost unit...hydraulic assist power brakes. Then the fluid goes to the steering gear.

It is rebuildable, but it may be easier to get a new one.

Civilian trucks have it also.

Memphisequipment.com for military parts.

Van