I assume you are talking about using them for the carbs.
I used them and they worked out OK. It's nice to do that with any aluminum manifold. I used some that were coarse thread on one end and fine on the other, but on the last manifold (not a 6bbl) I used 1 3/4" long allen set screws, but 1 1/2" should work too.
BTW, the Dodge is six pack, Plymouth is six barrel or 6bbl.