Question on guage wiring
....uh.....NO
But it depends on what you mean by "splice."
If you have an aftermarket mechanical oil gauge, you'll have to "tee" into the oil port to have the oil lamp and oil gauge connected. IF you have an electrical aftermarket gauge, you'll have to tee into the oil port and install the correct sender to match the aftermarket gauge.
Same deal, really with aftermarket temp. You'll have to figure a way to mount both senders if you want both gauges to work.