The special wrenches should be available at parts shop. However, I do it without them and I don't think it is much of a problem. I can't remember having any trouble with adjusting valves on cylinder #5 on a '80 300SD.
I suggest getting gage stock .001" smaller and larger than nominal and use them as go and nogo gages and adjust to the high side (clearance decreases as valves and seats wear). I use .003", .005", .013" and .015" gage stock.
Most important thing is to tighten the lock nut securely. I had a valve go thru a piston because someone didn't tighten the lock nut properly.
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