Yes they will. I just finished installing a mechanical coolant temp gauge and boost gauge in an A-pillar pod on my wife's Cobra. That said, I wouldn't want either of those you're talking about inside my car. I'd use a cowl panel setup personally.
If you want to mount an oil pressure gauge, use the copper tubing instead of the cheap plastic tubing that comes with the gauge. The parts house normally have the copper tubing in stock. Fuel pressure, you need to either get an electric gauge or use an isolator and then run the line to the gauge. The isolator stops fuel flow in the engine compartment and only runs water in the line inside the car.