Sorry for asking, but do I need the Control box after having swaped the engine? The new engine has its own harness.
This Control box ..comprises the voltage regulator and the cut-out.
Voltage regulator: regulates the voltage from the dynamo....
Cut-out: ...is really a automatic switch and connects the dynamo to the battery...
If you have an alternator on the new engine, then no you don't need the control box. You could of course leave it for 'period flavour' and if you remove the innards, the cover provides a good place to hide your spare car keys.
Ivor