I think there was a square piece of heavy gauge sheet metal tack-welded to the floor under the "jump seat" (maybe TrknGMC, or others, will post some info?)? I think that photos have been poster here, over the years.
Jim Carter sells a 47-55st Suburban upholstery set. Maybe you can find it in his on-line catalog. Or, call him.
There were two slightly different-width seat cushions used on 47-55st Suburbans (I do not know when the change took place). Jim Carter's upholsterer should have the patterns for both sizes. My guess is that 1950 would have the slightly smaller seat cushions (the size that JC normally sells)?
Also, Jim Carter's Suburban Suburban upholstery installation kit does not contain one of the original layers of "stuffing" material - a coir matting layer (some members have used a piece of heavy/firm-nap carpet under the top soft/fluffy-material layer).
