G'day Tony,
I'll presume the article you are referring to is that published in the RE Owners Club magazine The Gun, No. 89, in November 1990. The mods described therein are all well-proven, but as is pointed out in the article, it is worth remembering that if originality is important, only some leave no external evidence. Some I've done, some not, but intend to as and when.
The oilway across the crankcase joint and the drillway in the cylinder base face are the cause of all sorts of strife - definitely sort those.
The big breather is worth doing, but obvious. If this matters, less visual would be to fit additional breathers in a pair of the rocker covers (Webco in the US actually made some like this back in the day) and also vent the oil tank into the timing case as per the article. I've also seen an additional small-bore breather taken from the oil filler neck.
If originality is not an issue, another mod I have seen is to fit a modern spin-on oil filter in the return circuit. As well as improving filtration, this increases capacity and cooling capability. Pipework for this can be plumbed via mods to the oil filler neck, or by rerouting the return pipe via compression fittings out of and returning to the oil tank top.
If your bike has got that awful 'tuning fork' head steady from the top rear of the heads to the fuel tank mount, it will be time well spent fabricating a replacement one-piece plate bolted to the top of the heads, tying the two heads together, and with a vertical extension fixed to a lug on the under-tank frame tube - think inverted T shape. Later bikes had a similar arrangement in the form of two L-shaped plates, but the one-piece mod stiffens the whole thing up and helps prevent crankcase joint chafing.
There's a bloke in NZ who has done pretty much all there is to do on RE's - he may be along in due course to impart a little Kiwi wisdom - he knows his stuff.