Yo!! I just bought the oil gauge but where does the sender unit connect to?

 

The way that most people do it is remove the oil pressure sensor in the back of the block and buy a " T " connection at a hardware store and connect it there. One side of the T to the oil pressure sensor and the other side to your sender for the gauge.

I just bought a sandwich plate and connected my sender there.

It's up to you.

 

do no hang the oil pressure sending unit off the block.

Instead run a short line off the block (make sure to get the correct adapter...it's a 1/8 bspt thread)

then tee off to the pressure sender and to the pressure switch.

It's much easier though to get an sandwich plate. those will have a 1/2" npt , and your sender should have come with 1/2 npt adapter to whatever your sender uses.

(it's much cheape to replace a 1/2 npt to sending unit adapter than to fix your block)