510's were Pro Touring before Pro Touring existed. Since they were almost new, there have been modified cars roaming the countryside and urbania that could accelerate, corner and stop better than the commercially available products from Detroit, Stuttgart or Tokyo. A relatively mild 510 outcornered the 911's of the day in the early 70's, and several iconic racers spent time in 510's (Paul Newman, Bobby Allison, John Morton).
I have two (cause I know you wanted to know); an early '70 2 door receiving a SR20DET transplant, cage and R Compounds, and a '72 wagon getting the sleeper treatment with a non-turbo SR20DE, factory option mags, and every period option I can acquire. The 2 door will be the fun/track car, and the wagon replaces a Suburban as a secondary kid hauler.
Greatest thing about building a 510 these days is that you have to really want a 510 to build one. Little to no aftermarket support (in the US anyway) means that every 510 is different. I am a "look what I built" kind of guy (read: broke-ish) so just about everything on my cars was literally made in my garage. The reason I lurk Lateral G Forums is because these are the guys who are really innovating in the automotive world. Steilow, Schwartz, and so on CREATE, not copy. I learn stuff all the time that I apply to my cars. Funny thing is, most 510 guys don't get Pro Touring, and most Pro Touring guys don't get 510's. No worries, I never cared for clubs anyway
Love, peace, and axle grease...