There was a Kent Moore J-tool for removing the front half of the booster. It was basically a piece of box tubing and flat steel that attached where the master cylinder goes. Then you use a large adjustable wrench to rotate and unlock the front half. There is a picture of the J-tool and instructions for the procedure in the factory service manual.
If you are handy with a welder and have some scrap metal laying around you can make the tool easily.
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