I am highly experienced with this- Ill show you my Visa Bill ..
I started with a standard gage at the regulator under the car
Then , to verify i had fuel problems i ducttaped a gage to my widshield directly teed/piped to the fuel line - This worked the best
Then I bought a Nordskopf gage from Promax .. crappy customer service from the manufacturer, 200 bucks down the drain .. sending unit is bad .. they wont send me another ..
Then I tried an isolation style from autometer .. its like juggling
dogs trying not to spill the antifreeze / mixture ..
I got the isolated gage to work halfway decently with some luck but Id say try an electric autometer gage .. its worth it .