This problem is well known. In many Ford V8s the oil pump is driven by a quill from the bottom of the distributor. That quill occasionally fails. I'm no expert, but for a variety of reasons I would doubt such a failure would occur in a GT motor.
The clearances in the oil pump of the 289 OHV engine are extremely small, so, if a small particle (smaller that the pickup screen openings) enters the pump, it locks it up. The failure then happens as the pump stops and the camshaft and driven distributor keep turning, twisting the intermediate drive shaft. The last time, I replaced it with an ARP drive shaft, although, if it happens again, I'm afraid it will transfer the problem to a more expensive location. As a safety precaution, I install a new oil pump each time.
I agree that the GT motor would not have such a failure, but I agree with Lorenzo that a working oil pressure gauge is extremely important, not only because of the belt drive, but for any failure that might occur in the oiling system. The two gauges I feel are most important to any engine's livelihood are the oil pressure, and the oil temperature (not the water temp). Unfortunately, we only have one of these. A ammeter or voltmeter tells us the condition of the electrical system's operational status, and the water temperature lets us know if the cooling system is working [i.e, the coolant (water) pump is running]. A tachometer used to be a precautionary gauge to prevent overrevving an engine, but today's electronics seem to do this well enough, yet for racing, it helps us gauge our shift points. Speedometers are only necessary to let one know that we have entered the speed zone where we might be doing something unlawful. Regarding a boost/vacuum gauge, the only time I've looked at mine is when cruising, in order to keep the vacuum level high and thus get the best efficiency (fuel mileage) - If I'm in the boost range, my eyes are looking out the windshield, which seems more important at that time.
