This is the biggest myth out there. You are going to "protect" paint that's 50 years old, can still be shined up nicely & protect it with clear coat that has a life span of about 10 years out in the elements. Then the clear coat will peel & really look horrible & then you have to paint it.
There is nothing that clear coat is going to protect. If you have any bare metal showing on the high spots just keep it rubbed out & knock out any surface rust while running it out. Keep it waxed up and that helps prolong the surface rust.
There is a big difference in a little surface rust & flaky layers of rust from the backside of lower quarters.