I would probably use a glycerin filled gauge at those pressure levels ... just a quick search ... and it got 5 stars LOL...OK, grassdoc found a liquid filled gauge - 1000psi for ten bucks. I appreciate the effort to find something inexpensive and works but I can't recommend that as I have no experience with that product or the company selling it. it may work fine but I doubt there is any info about the accuracy, repeatability or ASME standards for which the gauge is manufactured or if the manufacturer is ISO 9001 certified.
My reference would be an Ashcroft 1005 series gauge to be configured by your choices...
No, for a notice for a maybe failing powermaster. The one that was on the car was failing (getting rebuilt) so in the future, I was going to have a heads up.You need a transducer connected to a logging device to glean any useful information over time. What you're building is a permanently installed troubleshooting device. Which is silly.