I'd suggest spacing the fan a couple of inches closer to the radiator and then installing a relatively short shroud. A fan blade should go half of its width into a shroud, so the point where the fan center meets the water pump pulley or the spacer should be even with the back of the shroud. Going further forward or back seriously affects the volume of air the fan can draw through the radiator.
Electric fans are noisy, especially if you install one that can move enough air to do any good. I'd much rather have an engine driven fan if at all possible. The thermostat sets the minimum operating temperature of the engine- - - -the size and efficiency of the radiator determines whether or not the engine runs at that temp or overheats. The only reason to pressurize the coolant is to allow it to go above the normal boiling point for the altitude and stay liquid. At sea level, one pound of pressure raises the boiling point 3 degrees. A 15 pound cap would let the coolant get up to 257 degrees before it boils, but the radiator, hoses, and heater core would all have to be capable of handling that pressure without bursting.
Jerry
