The most important thing if you are doing this is to get an alternator that is the same diameter as the original generator, otherwise you will have endless difficulty with the coupling.  You may be aware of the late Heidi Hestler who travelled the wolrd in her much modifieed '30 H8, and this was a constant problem as the alternator was too fat, and caused vibrations and  broken coupling bolts.   As far as L.E.D.  bulbs go, I was sent a pair for my Essex, but there was no difference in the beams between high and low, so I would be careful that  the bulbs you get comply with the legal requirements of having a high and low beam.   They certainly do give a brighter light, but the colour tends to be  a bit bluish, which can affect your eyesight after a while.  If you are converting to 12 volts be prepared for broken Bendix studs, springs, and much wear on the ring gear teeth.  

Thanks Geoff. My preference for the alternator would be to fabricate a new mounting bracket and mount it at the front of the engine. It would require a longer fan belt of course.
You kindly showed me your garage during my month long tour of your beautiful part of the world in 2017. I long for the day when we can safely travel again.