Just an idea for rumination...
I don't have a troop car to reference, so I apologize if this suggestion is too far off-the-wall...
1) If you have a straight floor to work with and its interior surface is flat...
2) If the added details (brake equipment, etc.) can be removed down to the bare casting...
then...
3) lay the floor interior-side-down on a flat plate...glass, metal, Plexiglas, smooth tile, etc....
4) build a shallow wall (Lego blocks are dandy for this!)around the casting with about 1/4" clearance all around, including about the same amount taller than the depth of the casting...
5) seal the walls to the flat plate with a bit of modeling clay...
6) Get some Alumilite RTV5 silicone molding compound, mix it, and pour it to the height of the surround wall following Alumilite's instructions...
7) Let it set up completely...
8) Take apart the wall, carefully lift the mold/floor from the base plate, and carefully work the floor casting from the mold.
then...
9) Lay the mold on a level surface
10) Mix up some Alumilite casting resin (I prefer the white...longer work time, thinner viscosity, picks up details the best....IMHO) and pour it into the mold (a shot of their spray mold release is a good idea...IMHO, again)
11) After it has set (don't be in a hurry to do this!! FULL cure really does take more time, per their instructions. Otherwise, warping may occur again, albeit easily correctable), carefully de-mold the part, clean up the flash, wash the part, prime, paint, reassemble, and add sufficient weight to the floor interior to bring it up to at least its original metal casting weight.
Just a thought. Worth a try??
Some enterprising soul (I would if I had the car!) could try this and, if successful, provide some replacements for others experiencing this problem.
As a side-bar, I talked briefly with Gary (Weaver) at York about the availability of the AFC trucks, something I need about 4 pairs of for a different project. He explained that the orders for the announced re-release of troop cars fell far short of the volume required for their off-shore builder. No cars, no trucks. However, all of the dies yet exist. To run them economically requires a sufficient build quantity. It's a common mantra these days, I'm afraid.
FWIW, always...
KD