Caution!
Rail Mount Fuel Pressure Gauges are prone to cracking and/or leaking which can be disasterous! If you do go with one, make sure you use steel fittings and not brass or other soft metal. An underhood fire can be a nightmare, assuming you don't burn your car up!
And ALWAYS keep an extinguisher in your car capable of putting out a gasoline fire (dry chemical at the minimum)!