Hi Nate,
there was a guy at Minyip or Murtoa, Vic,
that had a pile of late 50's through early 70's Chevs and Pontiacs, being 63 Bel Air's were reasonably popular over here, you should have a fair chance of getting your side trim mouldings.
If you look in Just Cars Magazine, trader "West Coast Imports" talk to Kym Kader (owner), he also has had many 63 Bel Air's, I know he has a bunch of mouldings, not sure whether or not he has any for your Bel Air, but give him a call.
Kym knows these cars intimately, and has a really nice 59 Sport Coupe (283). His daily driver is a 66 El Camino.
By all means mention me, been good friends for 30 years.
I have another mate who has a pretty tidy 63 Bel Air, I will have chat with him and put the word out. Some of those side trims you have look like 61, they might fit my 61 bubbletop.
bang