If you have new carpet I suggest that you use a soldering gun and melt the carpet around the studs and the insulation on the bottom of the carpet. Do it carefully to not melt any further than what the gas pedal will cover when it installed.
You can also remove as much of the insulation through the 2 holes for the studs( also not easy ). The purpose is to allow the gas pedal to fit completely over the studs( and not have the carpet push up on the bottom of the gas pedal).
cutting the carpet around the studs is very hard, that is why I switched to melting the carpet after carefully punching 2 holes directly over the studs. New carpet can not fit tight against the floor pan - marking cutting and melting the gas pedal studs should be the last cut “after the carpet is fit” to the tunnel, Floor shift hole(s) under the firewall pad, cut to fit the kick panel area, and checking carpet fitting under the sill plates
I have used this method on 5 - 62‘S with new carpet, no issues with the gas pedal falling off the studs( my gas pedal studs are Non pitted original factory studs, or NOS original GM studs
I used nothing but the best all rubber gas pedals with the plastic insert - I have 3 different ones for comparison that I saved ( I think there has been a decrease in quality of the Reproduction gas pedals over the last 10 years).
A rubber hammer is the best way to install the gas pedal( hitting base of the gas pedal, “as already stated“ make sure the holes in the gas pedal are over both studs.
Paul