I believe (I think I actually read it in an article) the reason Ford went with the oil pressure switch starting in 1987 (and it't still this way, my 03 6.0 and 11 3.7 is the same way) was customer complaints. With a sending unit and the gauge moving around, or the "I drove my buddy Bob's truck and his oil pressure was higher on the gauge on mine is, so there has to be something wrong that you need to fix" returns. If every vehicle has the needle in about the center of the gauge, they get less complaints. Remember, having a gauge for anything other than fuel or temperature was the norm. Even into the 70's and early 80's, a battery light and oil pressure light was common. I remember seeing the 73-79 Dentside Pickups and Vans, have a gas gauge, a temperature gauge, and a batt (or alt) light and and OIL light. They had to be ordered with a full set of gauge. 80 was the first year that all 4 gauges were standard. I don't think I have seen a bullnose with just lights, I think they all fad gauges. Think of how many complaints they received in 6 years. Plus, with with them still having the IVR, and the gauges having a mind of their own anyway, I can see why they went to a switch causing the needle to move to the middle. Most of the general public will enjoy the warm fuzzy of a gauge that doesn't move. Then even have moved away from have in all the gauges. My 2000 P71 had al 4, my 2007 P71 only had 2, everything else was a light. I think the trucks having gauges is mainly "trucks should have gauges". My 11 F-150 3.7 V-6 has" Oil Pressure, Coolant Temp, Fuel and Transmission Temp gauges. They are still the classic, no numbers, just a range that Ford normally does. But the oil pressure gauge comes up to just to the high side of center and never moves. The other 3 move. The oil pressure gauge is just a "light with a needle" Even on my 03 6.0 it even says int he manual when the oil pressure is above 7 PSI the needle will move to the center of the gauge.