I have been invited to a number of Pontiac Engineer Reunions and met the pilot (test driver) for the first 1964 GTO. They called him the pilot he was a pilot, but his testing of the first goat explains why things are different and cost more today.
He told me he took it around the perimeter road at what is now the Warren Technical center. It felt good so I kept going faster. I got it a little over 100 and said it was good to go.
Back in 1969 there was no EPA validation for 50 states, there was no crash testing, they didn't spend day after day in the wind tunnel, and the list goes on. Just think of the expense for crash testing the Z/28 due to lower ride height with the 305/30/19s. The vehicle cost is insignificant in comparison to the computer and lab time.