Heard stories about sales reps who would "drive by" other dealers of the same brand. and scope out their inventory. In the pre-internet days, it was either that, or make a few phone calls ("Hey, but do you have any half-ton V8 pickups in Dark Metallic Blue?")
By the '90s, it was easier for dealers to scope out inventories in other areas. When I bought my new Mustang LX 5.0 in 1989, the dealer looked at a sweep of other Ford dealers in north Texas, and gave me a short list of what paint colors were available, When I suggested that the dealer in my hometown had one in a color I liked, he called them, but the pinheads there told him that THAT car was 'reserved' for the local police department (idiots...I wanted it because it was a HATCHBACK! The cops were in line for a regular COUPE of the same color!). I eventually picked one of the available colors (Medium Cabernet Metallic), and the Fort Worth dealer put out a call to the small town dealer outside of Wichita Falls that had it (Park Ford, Iowa Park, Texas. Dealer shut down years ago). Dealer trade was arranged, and the dealer swapped a new F-150 Super Cab with the 'Texas/Oklahoma package' (5.0 V8/5=speed XL, factory built with the XLT seats, chrome grill and bumpers, fancy wheels. and an AM/FM radio),
Today at least with Ford, one can use Ford's website to uncover EVERY new vehicle in every dealer's inventory, in the state of Texas. One can use the info to either go to that dealer and buy the vehicle, or use their favorite and/or neighborhood dealer to do a swap. My parents did that for my dad's last new vehicle (2010 Ranger Sport SuperCab 2wd).