I think I got the answers I was looking for.

My oil pressure is reading 19 at idle and 25 at 70 miles per hour. The Chevrolet dealer says this is fine (note: this dealer did not sell me the car). Driving in Overdrive makes a difference as well.

Thanks everyone for the input

 

Your RPM to Oil pressure is more inportant then MPH to Oil Pressure. At idle 19 is still on the safe side. You may want to change your oil and filter and see if it jumps up. You should gain about 10 psi for every 1000 rpms. If your getting at least 50 at 6000 rpms then you should be fine.