NOS frame mounts will be hard to find and if you do find them they are big $$. There are eight rubber pieces total upper and lower. Also there are crossmember rubber mounts also. I can give you the part numbers for them if you want. You can get poly for them also. Personally I have the solid mounts in another car and they are too harsh IMO. It does handle better but I don`t like the trade off. I will be taking them out one day when I get some time.
Not a slam, but, how is the ride too harsh compared to a '72 -back? Having owned a '72 wagon and a '78 at the same time yrs ago, not once did I find the '72 offensive compared to the '78 (which was stock).
I guess it was for people like you that Chrysler went to the iso-K.
Me, I can live with the 'harshness' of a '72-back B-body.
Hmmm.....maybe you can swap out your solids and sell them to the OP to try out?