I managed to take the distributor (for my 66 122) along with the "box" from a 74 240 that had a B20 and auto trans. I found that the distributor had a vacuum retard. The box found a nice home out of sight up behind the glove box (tray)

But in examining it closer I found it was possible to arrange the parts a bit differently and flip the vacuum unit over so It worked as an advance.
I remember something about a little pin that is attatched to one of the plates. it could fit into a hole , or a slot in the other plate. I think I had to remove the screws in the top plate and rotate it to a different position.
I think I had to bend the tabs on the advance unit a little to mount it that way.

This wasn't a perfect solution. I had done enough work to the engine that I wanted it to run at higher than normal revs. I think it needs more advance. now I have it tuned so It doesen't ping up hills, and it accellerates nice at high revs, but is hard starting when cold, and runs like a dog till warmed up , then all is fine. It does have a good spark now though , and no more points, it idles way better that it ever did with the contact points.

It would be nice if someone could elaborate on what distributor to use , or how to modify one for a wider power band, eg shifting at about 6000. I can experiment with trial and error, but someone with access to a machine that could spin the distributor and look at the curve could do a better job, it is a bit of a science it seems , to get the distributor's curve to match the engine.

Phil