Questions about my gauges

[conoco]

My gauges on my 72 k2500 one of them is always pegged out even with the teuck off. The other ( my oil pressure gauge) sits on H every time I drive my truck. Is that where it is suppose to be? Everything is running good so I dont think there are any problems, just didnt know if I needed to fix this and how. Also, next to my oul pressure gauge there is a blank gauge, what is suppose to go there? Anything? Does it have a purpose? What should I put there. Thank you for the help.