Another thing to consider doing is to replace the lifters. My '88 300TE had one or two that were intermittently making noise (indicating that they were leaking down) so I replaced them. I just did the entire deal at 165k (head gasket had begun to weep a little oil out the back of the motor, and there was a tiny bit of oil in my coolant expansion tank), so I'm speaking from recent experience. And assuredly do the valve job while the head's off!
"If everything seems under control, you're simply not going fast enough" --Mario Andretti
1995 E500 street car
1986 Porsche 944 Turbo S track car