I asked some questions of the Ford Archives re: the Budd bodies and got this response:
Hi Todd,
Here's what I was able to find.
In October 1963, Budd Company provides engineering design services on proposed 1966 Bronco of body-in-white, seats, trim, and body electrical along with the majority of the body sheet metal components. (Edit - this is known info for Bronco historians. TZ).
In 1974, there is discussion around cost of sourcing sheet metal from Budd Company versus Ford’s Metal Stamping Division but it appears to be a hefty cost savings to continue to source from Budd. The record does not explicitly state that this is for Bronco panels but as a supplier to Ford overall.
As late as April of 1979 Budd Company is still listed as supplying sheet metal panels for Bronco, SuperCab, and Medium Trucks. However there were plans to reduce the amount of panels being supplied by Budd for the 1980 models.
Beyond 1979 I can't find mention of Budd providing specifically Bronco panels.
Hope this helps!
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Her answer doesn't explicitly state or give information that Budd produced the body panels for the 66-77 trucks. However, I infer from her 1974 statement that Bronco panels were likely included in the sourced panels from Budd, particularly since they were "still listed as supplying sheet metal panels for Bronco, SuperCab and Medium Trucks" in 1979.
I think it aligns with what the ex-Budd employees have told Nick.
Todd Z.