Originally posted by Tech @ BG
There are many companies that make small 1-1/2" test gauges. The problem you're going to run into is these are "TEST" gauges, they are not designed to be left in place. They have very small springs, and parts inside which do not hold up well with vibration. Most speed shops will keep 100PSI test gauges in stock.
Like I said go to walmart buy their oil gauge and install it any where under the hood. Now go back to sleep