The gauge should have a range of 0-100 psi.
The sender can be mounted beside the oil level window where there’s a large hex aluminium bolt, threads are 20 x 1.5. Replace this bolt and drill the new one to accommodate an 8 mm banjo fitting. Connect a steel braided line from the banjo to the gauge.
You can get all parts at a hydraulics shop
Normal oil pressure for the Vmax is approximately:
Cold engine: 4,4 – 5,6 bar / 63 – 80 psi at 1000 rpm
Warm engine: 0,25 bar / 3,6 psi at 1000rpm, 5 bar at 6000 rpm