valvetrain noise 5.9 magnum

If you have good compression, no weird colors on any plugs and no oil in the water/water int he oil, I'd just do the lifters.

As soon as you take off the heads to check you are gonna end up replacing them, even if it runs great right now they are currently cracked (they just are, the casting is kinda shitty, my 96 5.9 ran great on the bench but were cracked between the valve seats on at least two holes) and as soon you take them off you should replace them with some Civia or Iron Rams ($700-900) which have an updated casting.

Valve lifters can wear and die and you don't have to pull the heads to get at em, you can just pull the intake manifold and the valley tray, mine I was able to just pull out with the pushrods.