I stumbled onto one like that at an estate several years ago. Although it had sat for three or four decades the owner had done a modestly better job of maintaining the car(s) before he passed away. Here is a pic from the driverside rear of an original 289 Cobra that was there.
BTW the car on the far side is a Mercedes 300SL Gull Wing. Somewhere else in the garage not visible in this picture was a very early Ferrari California with a 100 miles or something like that on the speedometer. There were one off Rolls Royces an original Allard (next to the Cobra) and just so many exotics I can't remember them all.
This passenger side front view gives a sense of how clean these cars were.
If I recall correctly he also had 2 new Rolls Royce Merlin engines in cosmoline and enough spares to build a couple more. There were about 40 or 50 cars (I can't recall anymore) in the garage and a whale of very interesting way cool artifacts.
Stumbling into one of these garages is a trip through time like no other I have ever experienced.
Ed