I still say it wouldn't take long to tighten 4 bolts per seat, slide the radio of choice into a double din slot, and attach the dash harness and clip it in. Done. Just that alone would make manufacturing much more simple (cost effective)... 3 radio's x 3 seat choices x 2 dash choices (gotta keep the well loved Elgin in there) x 2 transmissions x 7 colors = 252 combinations that the factory would have to maintain... not to mention that there is NO WAY to build a car with NO notice and then ship it 2,000 miles without hella transportation costs. I believe the trucks spent about a day on the line including the paint booth. Let the dealer slip in the radio, clip in the dash, and put your seats in... the dealer could have 14 cars, 3 sets of seats, radio's, and dashes and be able to have your car ready within 48 hours easily-no matter which of the 252 combinations you picked. Shoot, if it was a slow day, they could have it to you in an hour or so(coffee breaks, naps, etc.). Every task I've listed was performed in 52 seconds or less at the GM plant. I know this first hand. I was an industrial engineer there and my job was to ensure each work station had fewer than 52 seconds per the GM standard time tables. Of course, they had a lifting jig for the seats but other than that, all these parts were quick installs that took literally one repetition before you could do it yourself.
Why is it so hard to think a dealer couldn't do it?... Though, I'll be honest and admit I've been to some dealers where I'm surprised they knew the difference between a manual and automatic transmission.
...And that's the way the cookie crumbles.