Oil pressure gauge
 

On my 79 Olds 403 powered Trans am the preivous owner put in after market oil and temp gauges and hacked up the wiring harness. My question is on the oil pressure switch there is a small tube which runs thru the fire wall and connects to the gauge. Does the original switch only use a electric wire tied into the harness plug that plugs into the gauge cluster, or does this tube coming out of the switch get connected somewhere?
Thanks for any help my manual doesn't address this.

Thats a mechanical gauge. The original is electric. You need install an electric sending unit and the wire runs off the engine harness to it

How does the temp plug in, is it on the engine harness also?
Thanks for the reply. I'm guessing that you can only get the switch thru performance years / year one type operations, or would autozone carry it?

Yes, it goes through the harness.

The oil sender uses a single wire that goes to the firewall
connector block, thru to the cabin harness connector, and then
to the cluster printed circuit (it's shown as "31" on the schematics).
Same deal for the temp sender, it's shown as "35".

I got my sender from PY. I don't think the local stores had it, but you can
try. RockAuto online is a good source.

Does anyone happen to have a picture of the harness set up they can send. I would like to put mine back original if I can.
Thanks.

oil pressure wire is blue, temp sender wire is green.

Don't know about now, but 10ish years ago the oil sender was still stocked in chain parts stores.

I did find a oil sensor for the gauge at Autozone. I have a 45degree stem from a 68 Olds 400 motor don't know if it is the same one Pontiac used though. Does anyone have a picture of the sender on their 403 powered Trans am they can post?
Thanks.