If the Faria gauges come with sending units then just install gauges & new senders & you'll be set.
If not, they may work with the original senders, you'd probably be best to contact Faria. Or just get new senders from them for their gauges.
You've got power to the gauges from the key switch & no movement when you ground the sender terminals, correct? And the senders check out?
Sounds like time for new gauges. There are some pretty decent priced complete sets if you google around awhile. Chances are the rest of the gauges aren't too far behind in konking out on ya.
Good luck
Jim