Keep in mind that the back of the gauge has a threaded fitting on the back, on the smiths repro gauge, it is a UNF thread and not American NPT, on the AutoMeter gauge it is a NPT fitting.
The pipe thread in. A standard ford small block / Windsor is a NPT fitting either 3/8" or 1/4" NPT at the block, or pipe from the block.
We mandate steel braided in our cobras, the plastic
oil line is bogus.
Steve