[wrndln]

What I do is use a large ball bearing that will force the top part of the D nut outward. I lay the ball bearing on the top, then with a large C clamp tighten the C clamp until the top part of the D nut spreads out from the force of the ballbearing being forced downward. The ball bearing needs to be big enough to force the top of the D nut outward so the top of the D nut can be hammered down tight. After the top is spread outward some, I do what Tom above does, finish the peening with a hammer. I don't think it is possible to get a perfect peen like Ford did, as I am sure Ford had special costly machines to set the D nuts, like Ford did with their fancy rivet squeezers.
Rusty Nelson