Dont have one for sale but when you do get one,
They are EASY as to install.
Just use the vaccume line that goes to your in dash boost gauge and stick that into your other boost gauge *assuming you get a mechanical one* From memory it was up the back kinda, near the firewall on the driver's side.
Then to wire it up, use the power source from the headlight dimmer switch, coz then your gauge dims with your instrument panel !!
OOOOHHH aAAAAHhhhh !!
Just earth it to some bolt on the firewall, or on the steering coloumn.
**see pic, thats where mine used to sit when i actually had a skyline
good luck, have fun