As far as the X-bracing goes, the vast majority of the original AD I see have or had them.
When I was a Chevy parts man back in the 50's & 60's we stocked and sold a lot of core supports to body shops. I don’t remember ever stocking or sending out a core support with a cross brace welded into it. When ever a vehicle gets hit in the front end the core support is usually bent out of shape. It's the foundation that the new parts are built upon or the datum point for you engineer types. This is especially true of the Advance Design trucks since the entire front of the clip is hanging off the core support and the whole shebang balances on a 1" x 2" bracket at the bottom of the support.
For a long time now I've wondered if the replacement supports were sold with out the X-brace because I've seen quite a few that look like they had been welded in after the e-coat was applied.
What I'm suggesting is that the core supports that we see that do not have the X-braces may just have had some front end work done to them at some time and the body shop skipped the labor of moving the brace from the old part to the new part.
Denny Graham
Sandwich, IL
