Actually, restoration in cases like this kill the value. Essentially, the studio sold it to the owner's dad in the early 1970s cheap. Back then, no one cared, there wasn't much in terms of nostalgia. It became his parents' daily driver. It was only fixed, not restored, original paint and dents. In the mid-1970s, Steve McQueen called offering to buy it, his dad refused. Some years ago, after his dad died, the son (the one who sent it to Mecum) took it. Last year, Bullitt Mustang #2 was found at a Mexico salvage yard, pretty much stripped - that one was severely damaged when it did the jump and became a parts car for the rest of filming.
TS