It's pretty much up to the builder/owner/budget on what gauges, if any, get into the car. Some come with zero gauges when built. Others, if the owner has a bit more budget, and really doesn't like rebuilding engines due to silly things like oil pressure loss, or overheating, will add gauges as appropriate.
There are rarely sanctioning body rules covering gauges, so it's up to the builder owner. They do add weight, which can be a concern if your class has no minimum weights, or you're having trouble making it.
Gene Beaird,
Pearland, Texas