Dave,
First and foremost, welcome to the website!
This group is not only a great bunch of people, there is a huge amount of information to be had here.
Bottom line like Paul posted, this Society is dedicated to the "preservation, maintenance, and restoration" of professional vehicles. We are mainly about preserving, maintaining and restoring these vehicles.
My personal opinion is that above all of that, we are about saving these vehicles!
Do some of our members have modified vehicles? Yes, they do. Are modified vehicles something that we strive for? No, they are not, but if you have a modified professional car, you will not be shunned. This society's main objective is originality, but we welcome all.
Hope you enjoy the site and the PCS as a whole!