Are these aftermarket gauges--what brand? Did the oil pressure gauge come with or have recommended a sensor? The typical OP stock sensor is nothing more than an on/off switch, doesn't read pressure per se.
When the proper sensor is in place wiring is simple from there, just follow manufacturers instructions.
BTW those are typically the first thing I disregard----don't need no stinkin' directions!
I recommend that you need to find a 12-volt ignition source and use the jumper wire to the Light Green/Red(not sure) wire. What that will do is it will energize the alternator when the ignition is turned on.
*******Alternator will not charge if you do not do this********.
by the way I am running autometer in mine. I could not get my alternator to charge at all before doing this I looked it up in the chiltons and florida 5.0 website.
Most aftermarket amp gauges require you to run all of the current thru the gauge.
I always used a heavy gauge wire to and from the gauge. Remove all of the wiring (except for the main battery cable) from the battery side of the starter solenoid and connect them to one side of the gauge. Then hook the other side of the gauge to the starter solenoid terminal along with the battery cable. once hooked up, turn on the headlights and make sure that the gauge goes to the - side of the gauge. If not, reverse the wires on the back of the gauge.
That being said, that was on a 71 Torino that only had a 65amp alternator. Not a lot of amperage compared to modern vehicles. What amp does the gauge go to? If only +/- 60, then I wouldn't use it.
They may offer something a bit safer to wire up, I would email them to see.That's why when I put a set of gauges in my 88 Mustang, I opted for the set with a Volt gauge instead of an Amp gauge. Just wired it to a "key on" blank spot in the fuse panel.
I also wanted a direct reading amp gauge, one that would exceed the 60 amp most common for autos/trucks. AutoMeter told it was their opinion (lawyers really) that said direct reading gauges in the 100+ amp range were unsafe since the high heat of enclosed mounting areas would cause problems.
While there are low amp draw gauge types that measure current far far exceeding what the standard automotive alternators produce they don't easily fit or mount into automotive installations. While the voltage gauges are basically "good enough" I'd still like to know what current is being produced but also know in this day and time anything of 60 amps just isn't available.