Being friends with many original ILMers has it's advantages with mental health approaches to these builds (for me anyway)... I am far far far less concerned with a part ID if it holds up a build. Life is too short, and they didn't and don't know what was used anyway. Not like we do! They find our "scene" interesting and are usually amazed we do what we do, and from first hand experience, I found it WAY easier and faster to make a model for Lucasfilm from key art than making a replica that needs endless research and rare expensive donors.
They did not treat these kits the way we do AT ALL. They were shapes. Shapes that would catch the light and look good on screen. Shapes that suggested mechanical actions and purpose. Each ILMer had a personal favorite genre, too. So you'd see Beasley gravitate to WWII German armor, Gawley seemed to liked the truck kits in those early days, and the F1 and car kits were picked because they were gear heads in real life. They were schooled by Johnston for the "guts on the outside" aesthetic, who was known to knock something off a model if he didn't like it, lol. Lorne said he would get in early to get first shot at the kit shelves (which were restocked over night) because he knew if there were five of the same kit in shrink wrap, he knew he would have five of the same part of he was doing something that needed to be a repeatable pattern. He said it was like making a mandala - and if you've done greeblie work like that, it IS very meditative! They would also rotate every 10 minutes or so, so that no one spot would stand out, on the surface of a model.