GM has used 80 PSI oil pressure gauges in a lot of applications. Most aftermarket gauges that I've ever seen are 100 PSI gauges. Also, most times I've seen higher end gauges in a truck, it's a higher end build that is far from stock and usually with an LS under the hood.
Which for me personally, if I'm buying gauges like this, it's going to be for a very not-stock truck. A hell-raising C10 with a 6 speed transmission. The kind that would benefit from a 140 mph speedo and an 8k tach. Like the other trucks I've seen and mentioned.