Rage

What is the maximum reliable output fuel pressure the first generation Merc Cool Fuel (pre 2005) pump setup can provide? Stock setting for a 496HO is 43 psi. The focus of my question is pump reliability / life as a function of higher fuel pressure regulator settings and not whether or not the pumps can maintain the higher pressures at higher fuel flow rates. Would 64 psi regulated fuel pressure cause a reliability problem for example?

PS I am not interested in hearing about buying bigger injectors or bigger/better fuel pumps.