Are you speaking of the governor support and gasket along with the tailhousing? Some of the older transmissions had rear pump gears in the governor support. These had to have a plate made to block off the main feed coming back to the governor, but with the JW case I don't think this would be the case.
It does sound like you do have a major internal leak causing the pressure to be low or the roll pin has come out of the relief valve in the front pump. The main pressure can be checked at the plug on the servo cover.
Bill M