Pull your original wheel and diconnect your horn wire..Bolt on the Tuff whel adapter and bolt the tuff wheel to the adapter.Then screw on the horn button and plug in the horn wire.It's real easy.
I don't know about the Mancine adapter, but I can tell you about the A body can.
Since the Tuff wheel was never offered on 67-69 A bodies, you'll have to use the later A body can. If you try to put it on the 69 column, the adapter will hit and just look wrong.
What I did was drill out the spot welds that hold the two halves of the adapter together and discard the lower piece.
This makes the adapter shorter but also the top half is closer to the size of the steering column, and it doesn't look as strange.
Here's a pic with the leather Tuff wheel installed.
When it's installed in the car, it's pretty unnoticeable.
I just installed a Grant tuff wheel in my 1970 dart (it's a Brazilian model, just like the 1969 American).
It's a three speed on the column and I used the wheel adaptor from Grant as well.
The install was pretty straight forward, just a couple of things to point out in my case:
The spring for the horn needed more tension to hold the horn button properly, easily fixed on install.
For some reason, I had to modify both my turning signal switch and the gearshift lever as BOTH were touching the wheel after install. Maybe I got the wrong adapter kit, but it was the correct part according to Summit. Anyways, some brute force and some bending fixed that issue.