My Autometer mechanical 2 5/8" gauge cam with nylon line, but it isn't very safe IMHO. So i picked up a braided steel line from Jeg's specifically for mechanical gauges. It isn't cheap ($50), but is worth it. It came with the right fittings for the block and to attach it to the gauge.
it has a line from the gauge to the block. the fitting for it is right next to the oil filter.
you basically either unscrew the stock one and lose the function of that gauge and screw the autometer one in, or some people get adapters to run both of them.
i am using the nylon tubing it came with and no problems so far