There are electric ones that have a sender unit... I dont know where they hook up but they are out there. Also, maybe consider putting the guage on your cowl right outside your window if you do end up going mechanical.
Are you planning on running nitrous
or do you just want to know your fuel pressure? To keep it cheap you should just put it on a Fuel pressure regulator right on your fuel rail, that will save you some money and youll still know what your fuel pressure's at.