The 3.5 heads don't have the oil passages drilled to the ball studs but I think a good machine shop could do it. Not sure about the cam compatibility. I guess if you have enough spare parts you could try it. You will lose lift and duration running hydraulic cams with solid ball studs.

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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