So, here's where I'm at. Oil pressure don't work, put a mechanic one on the block, obviously motor has good oil pressure. Install I new Livorsi gauge, 0-80psi. Hooke everything up, still don't work. Run jumper wire to the sender, still don't work. Touch it to ground, gauge jumps to 80. So that tells me gauge and wire to motor for sender is good. Buy a new sender at the auto store. Install it hook it up. Gauge now stays at 80psi!!!! Does Livorsi gauges HAVE To use a Livorsi sender? Or does the sender run a different ohms ? Any one have any ideas ?

Yes you have to use the correct sensor to match gauge. I just replaced my Livorsi oil pressure gauge. They asked if it was an 80 or 100psi gauge.

You need to have the correct ohm sender to match the gauge. Most of the time standard Merc senders work with the gauges.
It just depends on how much sweep the gauge has.

A VDO sender will make a Livorsi oil psi gauge run backwards.
Also, do not use sealant on the sender. It grounds through thread contact with the block.