Packard type 56 terminal end (male)

Just my opinion, I would be tempted(we installed a triple gauge set) to change to a mech oil psi gauge.
My reasoning....
I dont trust 60+ yr old gauges
under dash work is not fun
an aftermarket triple gauge set doesn't look outta place and it allows you to leave the oem gauges in place.

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Actually, I do trust 60 year old gauges if I know it's all wired and tested properly. This particular car has had the IVR replaced, all gauges tested on the bench too. It's the firewall connector giving me just a bit of a problem. I just don't like the look of aftermarket gauges hanging below the dash.