Duel booster break system trouble shooting

[Wade R]

Hello who's ever eyes land upon this. I seem to be having trouble finding anyone who might have knowledge pertaining to the dual booster break system that is on my 1981 gmc  B6000. This isn't the hydro-max nor the hy-power this is the dual power booster system that has a vacuum booster attached to the firewall followed by what I have found to be called the power head which is essentially a hydro booster but unlike the hydro booster it cannot be taken apart to replace the seals and O-rings.That is then attached to the MC. Any litterateur or knowledge one might have would be greatly appreciated!!! As of now I have found one picture of my exact system and it is a drawing from a catalog. Yet to find any literature anywhere

[Snowcamo]

Check gmsquarebody.com

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[Doug_Scott]

The era that was used was right in early part of my "career", and I have never seen or even heard of this system.  This truck used to be diesel?