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IRC, there were two different manufacturers of the power assist, Bendix, or Garrison. There "was" a user here that had diagrams that pointed out the differences between the two setups, but he is no longer here to chime in. Try doing a search for "power assist" maybe one of his old threads might pop up?
[edit] I just did a search, he set his album to private and re-arranged everything, so his links are all dead. There are still lots of threads covering power assist, how to fix it, why it sucks, and how to properly fix it by replacing it with a Lowboy setup.