i just bought a 84 trans am with a 305, i took it out on the highway an the oil gage jumps to 80+ any idea why this is happening once i get back into town an slow down a bit it drops back down to 60 and does anyone have any aftermarket headers they wanna sell

 

The oil pressure follows engine RPM, up to the limit of the relief valve. Therefore it is usually higher is always higher running on the highway than running around town. That being said, your oil pressure seems abnormally high, especiallyfor a 23 year old car. What weight oil are you using?