Oil Pressure Gauge install questions

If your budget is not tight, go with electric. Contrary to popular belief, electric
gauges now days are all more accurate than mechanical gauges, and no, electric gauges will not read wrong with lower voltage until you get so low
you are going to notice other more serious problems.

Mechanical problems, Large senders to fish through the firewall for temp, hot
oil inside car for oil. For a mechanical water, unless you already have a large
port for the temp sensor you will need to put in an adapter for it. Capillary
tubing for temp senders is a pain to run.

Mechanical gauges accuracy about 5-6% on a GOOD gauge.
Mechanical gauges, low cost.

Electric gauges have small wiring harness or wires to run through the
firewall and the senders will fit right into your current block locations.
Only wires running into the car. Accuracy of about 2-3% on a good gauge.
Better gauges auto calibrate at every start up.

Electrical gauges typically cost more due to the cost of the senders.