Is there supposed to be some type of seal or gasket that goes between the belt moulding trim and the body ?

It has been probably 20 years since I took the same molding off my car. There was a thick waxy like material between the molding and the sheet metal, almost like a bees wax. I remember it being gray/black.

You have a good memory! It was almost 8 1/2 years ago I took mine apart. I thought I remembered peeling something off there. I have a roll of that gray material you mentioned. looks like I'll be putting it on
Thanks

What is the gray stuff you are talking about and where can I find some ?
I am in the same process of putting on th moulding also.
Thanks!
Dave

When my grill chrome was done they used a dark grey silicone like bonder, more like liquid nails. 3M trim addhisive. some pieces have plastic clips, some crimp, or slide lock.

They used dabs of it along the way. Not a thick bead across.

Well im not sure if the gray stuff just goes where the trim moulding clip holes are or if it goes the entire length also still dont really know what stuff to use. Auto parts guy isint going to know if I tell him gray stuff LOL !
Thanks for the help !
Dave