Tom, I've replaced the lower windshield channel on my 66 GS. It's not terribly difficult. But the front fenders have to be removed to access the entire piece. Drill out the spot welds, clean it all up, and weld it back in. I have pics avail if you need them.
Before disassembly, carefully note the gap to the cowl screen panel, and the location of the screws. Then use that cowl screen as a reference when reinstalling the new channel.
Repo parts is avail for about $65. Chevelle channel is the same. The dash repair piece was different than my 66's.
