Ford oil pressure sending unit? Which one do i need?

So I'm trying to get the gauges working in my roadster and I'm kind of stumped when it comes to what sending unit i need. Im running 38 ford gauges that are being stepped down to 6v. I've looked and looked and i keep getting two different answers for sending units, a 50psi model and an 80psi one. Looking through parts books, i keep coming up with the 80psi, standard # ps-108. Is this the right one that i need or do i need to find a 50 psi? And would anyone have a part number for it if that is the case. Thanks, John