KELSEY HAYES PROPORTIONING VALVE KIT SOURCE

There was an adjustable valve that seems to have been used on some Fords and/or GMs that came with Kelsey Hayes 4 piston calipers. There's a photo of it in Mike Martin's book, and hence some might assume it was also an early factory Chrysler item.
This is all a side bar and I agree not really pertinant to the original question but worth addressing since its been raised.