Hi, Russ:
A few tips from someone who's only 6'2" and whose thumb regularly met my nose when I was shooting Dad's Remington Model 10 12 gauge back when I was a pup. They were Magnum loads of course. Why was I using Magnums for Mallards? Because they were there. A recoil pad and sensible loads made it a different gun.
Without seeing you, I'd guess you'd need about a 14 1/2" length of pull, measured from the trigger to the centre of the butt plate. I can't see how Jeff Cooper can shoot with a 12 1/2" stock, even though he's got a sturdy build.
The `97 Weaver catalogue lists the K6's eye relief at 3.3". Leupold's have an honest 4" in the fixed powers and some variables.
Your bench could be too low, making you lean into the gun, rather than sitting upright. Raise your bench with some 4x4s and a top of plywood, if necessary.
Push your shoulder ahead and up, giving your body room to flex and pushing the gun away from your face. If you're shooting offhand, raise your elbow as well. This makes the high shoulder position easier and helps keep your head upright, which keeps the balance mechanism in your inner ear happy.
A length of pull that's right for shooting off the bench in summer will be 1/2" too long for offhand shooting with winter clothing. It might be an idea to fit a thin rifle pad at the same time as you fit your recoil pad.
Try stacking a few of those black 1/4" spacers between the wood and the pad. Just be sure you've got your grubbiest coveralls on when you grind them down flush.
The other fellows gave you good advise too.
Bye
Jack