Truly adjsutable shocks

In 1969 I used air shocks on my dart to get different stability levels for the street and strip/. I had an air valve sticking out of the rear bumber near the license plate and I simply went to the gas station and used the tire airpump to fill up etc.

What exists today that will accomplish the same thing for my 69 Dart GTS 440?

THanks
Chas