Your description indicates that you have revision A of the card (M4091LL/A). Revision B of the card (M4091LL/B) is slightly redesigned and provides full compatibility in the 5400/120; installation instructions are also included.
The revision A card can be installed in the Power Macintosh 5400/120. However, you will first have to remove the Apple External Video Connector from the logic board of the Power Macintosh 5400/120.
Install the 7-inch PC Compatibility card into the PCI slot and insert the GIMO card (the small video board that's connected to the DOS card with a ribbon connector) into the slot previously occupied by the Apple External Video Connector.
Do not use the audio cables that come with the 7-inch PC Compatibility card for installation in the Power Macintosh 5400/120. The GIMO connector card also handles the audio signal.
Article Change History:
16 Apr 1997 - Edited rev /B information.