oiler for Lucas dynamos N/S end

[Parazine]

So should those particular bushes definitely be drilled or not? 

If the bush is original, it will be sintered bronze ("Oilite"). Some will have been replaced with solid bronze or brass bearings (they're easy to turn up on a lathe) and these should be drilled with a small hole. The problem is that excess lubricant will find it's way into the brushes area and generally mess things up.

As to the efficacy of ninety year old Oilite, well I'd be rather dubious.....

---

Is that "plug" not a gauze filter, usually painted over? I seem to recall similar on magnetos

No.