I want to do the same on my '67 and have been researching it. I think the deal is you need more clearance with disc brakes to clear the caliper. From what I could tell, the Torq-thrust D's are a thicker wheel (than the Torq-Thrust II's) and don't have as much room on the inside of the wheel. I was looking at the Torq-Thrust II because it seemed to be a little thinner profile.
I could be wrong though, but that's the impression I got from the reading I did.
I would be interested in seeing how it looks when you get them!