Looking at my Lucas catalogue covering the period 1936-57, E is eccentric mounted armature, 3 is 3" diameter, L is long type yoke and M is magneto mounted. It also lists a E3L for the NH range across those timespans, presumably as an upgrade to 60Watt output from the earlier E3H 48 watt output. It doesn't give any obvious explanation for your L0 or L1-0 suffix.
My experience is so long as the dynamo is compatable with mounting on a magdyno magneto, and has the correct 22t drive gear, it doesn't matter too much. Output/rotation can be altered by swopping the position of the brushes. I have rebuilt a number of dynamos on this basis.
The earlier drive gear was widened to suit the 60w dynamo and wider fibre drive gear on the magneto, Ebay offerings are usually the narrower type, although they can be used with the wider fibre wheel, it just loads a smaller area of the gear.
No doubt an expert on Lucas electrics may be able to improve on my observations above, but as a rule of thumb they should be helpful.
I have upgraded dynamos on previously owned Ariels to 12v by just purchasing an electronic regulator, and although this did not give me any particular problems, I think there is a risk if you use the outfut to the maximum frequently. There are 12v armature/field coil conversions available, I think these give greater output at lower rotation speeds. My magdyno single was fine, but my Huntmaster would not balance the QI headlight until 40mph.