Squeaking Sound Coming from 225 /6

I'm just going to go ahead and ask, how would i install a mechanical gauge, is there one in particular i should get, etc. I know very little about installing gauges aftermarket but im open to learning

Just unscrew you’re oil pressure sending switch that on your engine now . Then screw your line or fitting to that hole . Then screw the mech gauge onto that !! But before you do anything drain your oil and I would cut the filter open and see if there is metal in your oil and filter !!