fuel pressure gauge install

how does an electronic fuel pressure gauge hook up? i have some guy asking me if i can put one on his 2003 cobra but i don't know what to charge him so i can't give him a price quote.

i've never put one on so i don't know how they hook up. can anybody shed some light on the subject for me?

i know they have a sending unit on some sort but where does that tap into the fuel line?

alright cool, that's what i thought. i just wanted to make sure that it did tap into the schrader valve. thanks man.