I'd say its either body posts or the lower portion of the body that needs further trimming. Either way, I am sure your friend has it figured it out if he's done this a few times like you mentioned.
I am currently painting up '71 camaro body for a VTA car I am building. I love the challenger, but had to go w/ the '71 camaro as my dad had a '70 1/2 camaro ...he bought it the same month I was born (almost made my mom divorce him as they couldn't afford it). LOL. But we had that car for years, many good memories.