I'm here to offer the opinion that you are better off getting the CHT to work. This is based on the potentially faulty notion that the 3.2 motronic used CHT, not oil temp.
I liked your solution but remember thinking it wasn't going to work but keeping my (possibly wrong) opinion to myself. Mostly because you'd already done a pretty excellent job with this and had it wrapped:
I don't know that you'll get the heat effect you need, by clamping onto the cooling fins, which might already be cool, plus there's a bunch of cooling air being blown right at the sensor and mount..... but adding some heat transfer compound might help the situation. Relocating it to a hotter spot might help.
Next, maybe a bit of tweaking of the correction tables or map or whatever is supposed to happen as the sensor heats up is in order? I mean, as long as you are getting some sort of signal out of the CHT you should be able to work with it?