MSD in these circles stands for Might Suddenly Die. So be forewarned. 
The original dual point distributor is a very good unit but if you want to upgrade to solid state, then the Ford Motorcraft is a much more reliable solution teamed up with a Pantera-electronics engine ignition controller.
That as considered as a unit is all plug-n-play and provides for the tachometer connection without an MSD adapter.
If you are here looking for advice, I'm just reflecting upon my 40 years of Pantera ownership and 55 years of Ford performance cars.
You didn't ask specifically this question but I consider it a synonym. A word that is not exactly the same but similar. I feel the question coming. 
I like your testing method, it is clever, but in addition these tachs are showing a need to be cleaned and often need to have the jewel movement of the needle lubricated. It's just their time to show it around now. The two that I had tested were off about 350 rpm and needed to be calibrated also. Pantera-Electronics can check the tach and calibrate it for you.
There has been quite a bit of discussion on this forum on subjects that all revolved around the distributor and ignition upgrades. If you are data driven, you would be wise to consider what I say but then again, I'm not highly intelligent, just highly experienced and my mistakes have yet to be lethal. 