If you are using a mechanical gauge that receives pressure through a small tube, just go to your local hardware store and pick up a few brass fittings that will thread into that hole in the pump and reduce down to the compression fitting for the gauge's tube.
I ran both idiot light and gauge for a while. I installed a brass tee in the pump, put the sending unit in the side leg of the tee, and reduced down on the other outlet for the small tube for a gauge. One word of warning... make sure you use a HIGH quality gauge or you may be asking for trouble. There's nothing like having hot, nasty engine oil dripping out of your gauge into the carpet. Fortunately, I had my gauge installed under the hood where I could watch it during cam break-in and tuning. It wasn't long before oil began to fill the gauge behind the dial glass and started leaking out the housing.
You get what you pay for,
Jerry
