Just throwing my two cents into the discussion here;
I am running NKG BP6 plugs, as recommended by Ken Grey at Dave Bean. He specifically recommended against the BP7 for road use claiming plug fouling could result. The BP6 plugs are definitely a better choice for my car, though my worn carbs are running a bit rich which makes the plug's job a bit more difficult. When ignition performance is not up to snuff I do incur plug fouling.
My Twin Cam is all original including the points ignition, but with a Lucas gold sports coil fitted. I typically run my point gaps .025" - .026". I check and gap my plugs often, occasionally playing with varying plug gaps when in an experimental mood, especially since the addition of the Lucas gold coil.
I also fiddle with points a lot, and have fitted many sets of points, and never remove the carbs to do so nor ever felt the need to. You get good at it after a bit, and have done them on the road side on a couple of occasions. I good inspection mirror and flashlight is necessary. Remove the boot tub to gain good access. Mine is not fastened in place and is easily pulled out when needed. John's suggestion to put the car in high gear and move the car to turn the engine works a treat, though I do this somewhat differently; I put the shifter in high gear, then place the pad of a floor jack under the RR lower spring mount and jack the RR wheel just clear of the floor, which permits me to rotate the wheel whilst peering through the window in the bellhousing to put the engine in the position I desire for points setting, timing, etc. Pulling he plugs first makes this much easier, though with a 5th gear it can be done without pulling them.
The points on the market today for these ignition systems are garbage. Most of the point sets I buy come in the Lucas green box, but do not expect OEM quality. The production has all long since been farmed out to the lowest bidder. The little green boxes contain point sets in one of two distinct variants for the part number. When I open a new box either set could be in there, and I have come to refer to them as the 'bad points' and the 'ugly points', the bad points being the preferable variant. There are numerous visual cues to tell them apart. I have had several sets of the 'bad' points lose their gap quickly due to rubbing blocks that are not square with the cam and rubbing blocks that when viewed with an eye loupe have significant porosity. I have had two sets of 'ugly' points fail prematurely, one set only went 30 kms before failing outright, and a third set I couldn't even install because the threaded post had deformed threads. The 'ugly' points also burn and foul the contacts quickly. I currently have my highest milage set re-fitted, from the summer of 2013, because they remain my most reliable set and all of the remaining sets I had in stock were either failing or deemed not worthy to install. I now have six new sets I bought from Dave Bean last year that are reportedly of decent quality, but haven't tried them yet. They are the only sets I have bought that did not come in the little green box.
Another note about points; The 23D distributor used on Twin Cam engines was used in many other applications as well. However, the points specified for Lotus and Cooper applications use a stiffer spring than the more mundane applications. It is difficult to tell, but I imagine that the vast majority of point sets available to us are of the softer spring variety, despite the fact a part number for a Lotus application may have been ordered. This will likely effect ignition performance at higher revs. I forget the actual spring rates, but if I recall the regular spring is a 28oz spring vs the Lotus/Cooper variant which I believe is 32 oz (Please do not quote me on these spring specs as I may have gotten them quite wrong).
