Gather up all the parts you'll need. Don't forget a large jug of BRAND NEW brake fluid too. No reason to use some old stuff that's been absorbing water for years.
First is removing all the Powermaster stuff.
Standard safety stuff here... Make sure to depressurize the system (odds are if you're doing his is because you don't have any pressure in there. lol), And keep some rags handy to mop up any spilled brake fluid. It makes plastic look good but will eat up some paint!
Once the two electrical plugs are removed, take the two brake lines and two mounting nuts loose. I find that vacuum caps make great seals for the exposed brake lines.
Next, remove the under dash cover and remove the clip that holds the Powermaster rod to the brake pedal. It helps to have a second person under the hood to move the Powermaster but it can be done alone. After it's disconnected from the pedal, it can be removed.
Then remove the adapter plate that converts from the 4 bolt mount on the firewall to the two bolt mounting pad for the Powermaster.
This little part is the reason there's two different pedals. It causes the Powermaster to point down a few degrees and as a side effect causes the pin location on he pedal to be higher.
While you're under there, remove the pedal as well.
Install the vacuum diaphragm and master cylinder.
Notice the front and real lines have been swapped relative to the Powermaster. Front is not rear and rear is not front. Much like doggie style.Luckily, thanks to the additional spacing of the booster one of them lines right up. The larger of the two lines need to be curled up to mate with the front of the master cylinder.
If you trust yourself not to kink the lines, it can be bent with your thumbs. If you don't feel that confident you need a tubing bender. Oddly enough the ones you can rent from the auto parts store wont' work. The one you need comes from a home improvement store like Home Depot. That one will go down small enough to handle the small brake lines. It can be found in the plumbing section.
Once the line is tweaked it can be attached to the master cylinder.
Once the pedal is out it can be modified to accept the new pin for the vac brake kit.
Measure 1-1/4" down (center to center) and closer to the edge. That is the new location for the pin. Notice the edge of the pin is now parallel with the large flange on the Powermaster pin.
Drill a 13/32 hole at that location. Then drill that hole out to 7/16" but ONLY go 1/3 of the way through. This is to get the pin started so that it can be pressed into place.
Put the pin on position with the cotter pin hole facing vertically and miss the Powermaster pin. Then smack it in place with a framing hammer. ...or if you have an arbor press, press, or vice I guess that will work too
Note: This is the "no weld / press fit" method. If you have a welder or a torch, feel free to start out and 7/16" and weld it.
Once the pin in installed the pedal can be put back in the car. Notice with this method the car can be returned to stock without having to drop the pedal again. You also don't have to lose sleep at night and feel shame knowing there's a Chebby part on your Buick!
Next is to run the vacuum line to the engine. Route the hose under the coil pack and tee into the PCV hose. Put the check valve before the tee. That way you'll keep from sending boost into the booster and it'll also keep boost from hitting the PCV valve. Bonus!
Another way is to get a aluminum vacuum block for the throttle body that's set up like a TTA with the vacuum port sticking out the side. I don't really care for how those look but to each their own.
Now that all the connections are made, all that's left is bleed the brakes and do a final inspection.
Now is also a good time to toss the 30+ year old rubber lines and upgrade to stainless lines. Not only would it be a safety upgrade but a performance upgrade as well. Since the system is opened and needs bleeding, it would be the perfect time.
All you have to remove is the wheels and they're already off.