Should be relatively easy.
You'll need a charge coil (also known as a lighting coil) under the flywheel - this may or may not be an integral part of the a ignition coil assembly. If it is, the tell tale will be wires from under the flywheel that don't connect to anything, if you find that, you probably don't neeed to buy one) Fun bit is removing the flywheel if you donlt already have the coil under there.
Then you'll need a regulator / rectifier. This is where I can only guess as to whether youll need one or two bits - some systems integrate both into the one lump of plastic, others use separate components.
Then all you need are a couple of wires to your battery - and if you aren't using a starter motor they can be sensibly thin.
If you can let us know the serial number, there are microfiches on Ishop, which hopefully will confirm the answer to both these questions.