I've had some Mopar motors that have carried 60 psi + at idled when cold and could drop to 25psi once warmed up. Those motors cold, at highway rpm, could get above 80 psi until the motor warmed up.

I'm a big fan of mechanical gauges, the factory gauges (nearly all are electrical with non-numbered faces) sort of give you an idea if something is out of the normal, but you really don't know exactly what you really have. To put things in the proper perspective, currently, everything I own is using the factory gauges, but back in my younger days, everything had mechanical gauges. (I have AAA towing these days, working on something along the side of the road isn't going to happen). Back when I had real gauges, I liked oil pressure, water temp, and amp/volts (if I had to eliminate one, the amp/volt gauge would be the one to go). Trans temp is another option given where you live, but you would have to install a sending unit into the trans pan. Those gauges can be mounted at the bottom of the dash, or sort of out of the way, you probably won't be looking at them all the time, they are a reference point if you suspect something is not right, or they are some thing you check occasionally to monitor what is going on. If you are going to peruse the best gas mileage, that vacuum gauge would be a great addition, put it someplace you can see it easily while driving, like on or near the top of the dash.

Gauges can get costly pretty quickly. I would tend to stay away from the cheapest gauges you can find, but you probably don't need the most expensive gauges either. Cheap gauges tend to have a shorter life span and some have inconsistent or inaccurate readings issues. Shaking and vibration are most gauge downfalls, more expensive gauges tend to reduce the effects of vibration, careful mounting can also reduce the vibration the gauge sees. The next most common issue with gauges is damage to the mechanical tubing, careful mounting and tube routing can solve a lot of those issues, the tubing does not like sharp bends, or sharp edges and has to clear moving parts that can catch the tubing. Gene