The QA1 Pro-Coil coil-over kits for the 1964-1972 GM A-Body and 1978-1987 GM G-Body will work with the factory a-arms or any of our tubular a-arms. The QA1 coil-over shock mounts to the a-arm the same as the factory shock, with a t-bar mount.
If you have purchased our tubular a-arms with spring boxes for factory type springs you can still later on run the QA1 Pro-Coil set up. The tubular a-arms we make that are a "coil-over version" have the spring seat for factory style springs eliminated for further weight savings, that is the only difference.