Federal pump has a tapped hole in the end of the pump shaft.
TRW/Thompson pump has a hex-shaped hole or no hole in the end of the pump shaft.
Federal pump uses a reservoir cap with "ears" much like a radiator cap.
TRW/Thompson pump uses a reservoir cap that is round and may have vertical serrations but no "ears".
NOTE: Federal pump reservoir cap will fit on a TRW/Thompson pump.