I'd hate to see you ruin anything. You are aware that, on the 65's/66's, there are 2 hidden bolts that you access them from under the dash. On the passenger side, look for a rubber plug near where the anntenna wire comes into the car. The drivers side has one in the same area too.
And, try not to fill the vin number on the inner fender panel with paint. I like to see the vin number for real. Otherwise, folks think you are trying to hide something.
You can loosen and then mask off the upper fender rail to avoid overspray if you want to avoid fender removal. Be advsied, the installation with lining up of the gaps will take a lot longer than the removal.