My 235 six is smoking out the tailpipe, sugestions?

[rustic]

MY 61 WITH A 235 SIX IS SMOKING OUT THE TAILPIPE. I KNOW IT IS FROM OIL BUT MY COMPRESSION IS AROUND 150LBS IN ALL CYLINDERS. I KNOW THAT IT COULD BE THE VALVE SEALS BEING THAT THE TRUCK SAT FOR A LONG TIME AND THE SMOKING IS GETTING WORSE THE MORE I DRIVE IT. I WAS WONDERING IF IT COULD BE SOMETHING ELSE CAUSING THIS. IF IT IS THE VALVE SEALS HOW MUCH OF A PAIN IS IT TO CHANGE THEM AND WHAT IS THE BEST WAY TO GO ABOUT IT. ANY HELP WOULD BE GREAT