I just posted a drawing for the P&LE 10500-10999 gon series in the STMFPH files section.
http://groups.yahoo.com/group/STMFPH/files
The drawing shows the construction and rivet pattern for the riveted steel floor. There are interior photos that show the nailable steel and riveted steel floors in the Greenville gon article in Railway Prototype Cyclopedia Vol 3, pp 52-67.

Larry Kline
Pittsburgh, PA