I really think the job would yield better results if you pulled the head. It probably would not take THAT much longer, you could check the valve guides(most probably worn out),de-carbonize the head/valves(if it has been burning oil it will need it) and evaluate the cylinders for wear to see if it is a candidate for new rings. If the valve guides are worn out, new seals are a short term bandaid-it's a lot of work to change them without knowing the condition of the guides.

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Tony H
W111 280SE 3.5 Coupe
Manual transmission

Past cars:
Porsche 914 2.0
'64 Jaguar XKE Roadster
'57 Oval Window VW
'71 Toyota Hilux Pickup Truck-Dad bought new
'73 Toyota Celica GT