I to got the Dynamregulator kit on the SA. It's a real improvement, well worth the money. On the SA the standard dynamo keeps the battery on a healthy 12V
So happy with it that I also ordered the same kit for the plunger.
I removed the chain sprockets with a small pulley extractor. For strength I left the chain on while pulling. Just watch out because they can be real tight on the shaft (mine where) and let go with a bang.
I first put on and tightened the drive pulley, then dynamo pulley on finger tight, laid on and tightened the belt and finally tightened the dynamo pulley. Don't forget the cork washer behind the large pulley (soak it in oil first). It's got to be lightly squashed between the pulley and the case for oil tightness.