Flat Battle Grey?

The official requirement at this time was "above the level of the instrument panel, instrument black, below, interior green." Interior green is green, as opposed to yellow, zinc chromate primer. I'd be inclined to paint the floor interior green and everything else flat black, with some white in it or drybrushed with a flat dark grey.

One fairly good set of black and white -1 photos seem to indicate that the seat, and fuselage sides above the side consoles are interior green. Tops and sides of the side consoles are black.

Flat battle grey is from Testor's little 1/4 oz line of paint. It is a dark to medium grey.

The interior cockpit color changed right after the post war period to dark gull grey. You might want to do some research on if the Bearcat has dark gull grey or interior green cockpit areas. Many planes around this period still have interior green/zinc chromate gear areas but with a dark gull gray cockpit area.