Alright, the CDI module is installed, although as I'm still sort of in experimental stages with it I have finalized it or prettied up my wiring yet.
Picking the correct terminations for the wire made installation super fast and easy. I used plastic shielded automotive grade quick connect connectors for most of the connections. Since the factory wiring loom is set up to make heavy use of these, wiring was plug and play. Completely bypassing the CDI box is also a straight-forward roadside repair with two pieces of wire(now in my spare parts kit) so I also have that option.
By far and away my biggest hurdle was getting a good ground. I put a spade on the end of the ground wire and ran it through one of the pre-existing screws into the body under the hood. The bad ground would show up as a misfire at high RPMs(where the CDI box draws ~4A) and would disappear when switched over to Kettering ignition(which does not even need the ground wire connected with the CDI box). Finally, I ended up using a wire brush on a dremel to clean the paint and oxidation at my grounding point and then slathered dielectric grease over it after making the attachment. I still want to go back and replace the spade with a ring, something that I think will be a lot more stable over time.
Also, Smiths internal loop RVI tachometers do not work with CDI ignition. Unfortunately for me, that's exactly what my car has. In the stock Kettering set-up, the +12V for the coil passes through the tach. In 1973, MG switched to using a Smiths RVC type tachometer, and through the '76 M/Y it was the same size with an identical gauge face to the stock tach in my car. The only difference in the bezel, but fortunately the bezel simply has a bayonet mount so swapping the bezel is easy.
The stock wiring for an RVC type tach is different than that for an RVI type, and wiring for the RVC is different still with the CDI installed. In a conventional set-up, the RVC tach is supplied with power and ground through the normal behind the dash wiring, and then a signal wire runs from the positive side of the coil to the tach. As I mentioned, on an RVI tach, the +12V side of the coil is powered through the tach, so there is an additional ignition switched(but unfused) +12V wire behind the dash. With the CDI box, the RVC signal wire is attached to the distributor body.
I do not like modifying factory wiring when I can avoid it, so elected to use what I had available. First, I pulled out the old RVI tach. The wiring is not completely plug and play with it. The +12V coil wire is a female bullet, so can be safely disconnected and left dangling without any worried about it shorting. The power wire(ignition switched, fused) is a quick disconnect connector, so simply plugged in. The RVC tach I have is set up to use a quick disconnect for the ground, while my old tach was designed to ground via a ring on one of the attachment lugs. I preserved that arrangement, but if it proves to be unsatisfactory I will run a wire from the quick disconnect lug to a ring that I butt up against the factory ground(the quick connect ground tab is just riveted to the tach body). It's not overly critical, though, as the RVC type tach only needs ground for the light bulb and not for operation. My only other hurdle was the signal wire, which was terminated in a male bullet. The RVC tach also has a male bullet for the signal wire. I though it would be a simple matter of plugging a male-to-male joint on the back of the tach, but ran into trouble as the male bullet in the factory look is smaller than "standard" diameter. I have a temporary solution now for testing purposes, but in the next day or two(once I find my stash of bullet connectors) am just going to solder the correct sized bullet in place. I also need to stock up on bullets-I'm getting a bit low, and it usually takes me about a month to get them from England(they are much less expensive there than in the US).
Under the hood, tach wiring was simple. When I'd built up all the connections on the CDI box, I pigtailed a second wire onto the connector running to the distributor and terminated this with a male quick disconnect(again automotive grade, fully plastic encapsulated). This went into the former coil +12V wire that's now the tach signal wire. The tach works, although I think the calibration may be a bit off on it. I'll hook up an external(inductive) tach and see what's going on.
So, the end result of all my rambling-
1. I have a smooth 850rpm idle-something that I couldn't get with points ignition.
2. The throttle response is better. It's not a huge difference, but to someone who has been driving the car as long as I have(and to have not changed anything other than tweaking the idle speed) it's there.
3. Cold starts are easier, and hot restarts are now a LOT easier. There's no more flooring it to get it to start when hot.
4. The plugs look perfect
5. I've learned a valuable lesson-don't hold the HT lead while cranking with CDI engaged

. Check for a spark with the HT lead held close to a body ground is a long standing technique for checking for a spark in a points-type ignition system. For a system in good order, a pale blue spark will jump 3/4" or so. The CDI spark is bright blue and will easily jump more than 1". The spark also makes a very loud crack-something advertised in the promotional material. Unfortunately, after half a dozen sparks, I found that they preferred to go to my hand rather than the body ground. That was quite an electrifying experience

. On the other hand, with the distributor body now at 12V rather than the ~300V in conventional points ignition, the bare metal can be touched without "buzzing" you. That makes timing adjustments easier.