Two things here to consider:

1): You can just wire the chain to the sprocket, remove the bolt (use a large screwdiver or something similar to keep the sprocket from turning) and slide the sprocket off. Wire it up when you have the head off to keep the chain from getting out of control.

2): This engine did not have the steel inserts for the head bolts installed at the factory. If the threads are seized on the bolts, the thread will come out with the bolt and you will have to install inserts to re-install the head. This requires a special jig to get them at the correct angle, and is rather expensive (jig was $1500 a while back). I'd talk to an independent mechanic familiar with this engine before tackling this job. If he feels you need to have the inserts done, I'd let a shop do the valve job.

you should also consider a chain conversion, too, if you still have the single row chain.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!