Still looking for the clips and springs if anyone has a lead I'd appreciate it very much.
I have built a number of these trucks, and to be honest with you, some of the trim still had the clips and spacers, and some did not, but I did not worry about it one bit.
It is next to impossible to see whether they are in place or not once the trim is in place.
Furthermore, whether they are there or not, the defroster works as designed. Quite well for melting frost, and very poorly for eliminating fog on the inside.
In theory, it might be good to have the solid "spacers", as I believe that they actually act as dams to help direct all of the air through the openings in the trim directly above the ducts.