To much oil+cold=really high oil pressure?
 

my k5 was running about 70 psi on the oil pressure gauge at school a few weeks ago when we started it when it was outside for about a week. i didn't let it sit and warm up. i just drove it into the shop and shut it off. my question between to much oil and being cold could the pressure be this high. i believe its running a heavier weight oil and i believe its overfilled by about a quart from previous owner.

70 psi when cold shouldnt be a problem.......a small block should run around 60 psi normally...change your oil to a good 10w40 and everything should be good. how many miles do you have on the 350 ?

well im not sure on the miles. originally it had a 6.2L and now it has a 350. according to the odometer it has 43,350 miles but im thinking its rolled over at least once (the odometer not the truck)

IMO you're always better off being a "LITTLE" low than overfull. But that being said the cold is probably more the issue.
I'd go ahead and perform an oil change and fill it to proper levels and see what you get. Also check the pressure independently of the gauge on the dash as the gauge maybe suspect.