Got my replica of the Belgian-style GPMG Mounting Kit almost done:
The main pedestal attaches to two 3/16" thick 5x8in plates bolted thru the floor and under the body, via a piece of 1.5" OD 0.25" wall tube welded to the plate, and a 0.25" dia clevis pin.
It still needs a secondary attachment under the glovebox for stability, elevation wing nut lock assy and the pintle lock assy installed.