My 69 has the guage package - not sure if it is original or installed afterwards. My oil pressure guage doesn't work, instead the previous owner ran a mech. oil pressure guage. I'd like both to work. Which sending unit do I need, the big canister looking one, or the one that more resembles a sparkplug? Right now the mech. guage is tapped into the galley (driver side). Where would the new unit tap into - above the oil filer?

Thanks