This!
And a leak down test

 

I have to agree, and a leak down is definitely a good thing to do too, will tell you if it is a valve seal or a piston ring or something else more/less serious.

 

pretty sure your right.given its not smoking under load or all the time. SO.. my situation. do to my most current incident.. i purchased i 03 ram 2500 parts truck, for body parts..lol great deal couldnt pass it up. knowing the popular body style an all figured i could part out an what not for other people. but has running motor trany.. and is drivable.. most likely spun a bearing cause has a pretty hard lower knock.BUT does not smoke. was wondering if it would be easier to switch heads or should i go ahead and rebuild my head with new valve guids and springs since their also known for breaking.since im already taking it off. given i have very little spare time but i know quicker isnt always better.

 

If the parts truck has less miles on the motor I'd rebuild those heads and swap em out for less down time. Lots of shops will check out heads for you for pretty cheap. I always get mine checked by an older machinist, he knows where the weak points are on ANY head I've ever taken him.
If you don't know already, you'll use exhaust valve springs off a 6.1L hemi all around on the heads (on the 5.7 intake/exhaust are the same length)
My vote is also valve guides, I'm going to have to do this on my truck soon as well.
Not to hyjack the thread, but how long can you run a truck with the seals going?

 

250K miles. Your valve guide seals are worn if they have never been changed out. I can guarantee that one. Also could have some blowing by the piston rings which is not a big issue as long as it's not excessive. I get the same issue with 210K miles on my '03. Just don't have the time to take each valve spring off and change the seals. I got them sitting on top of my tool box (been their a year now...lol)

 

As long as you keep checking the oil and topping off between oil changes.

Not recommended but still can be done.