I have not seen any list of conversions done to an AV. The only one I know of that was an aftermarket company called Southern Comfort Conversions and they came in several colors that had a fade or hombre paint pattern with painted upper cladding to match. They even sold painted upper cladding parts with sail panel LED Light bars to tie in with the 3rd brake light. I don't believe they had anything special for interior customization though.
I don't think Regency ever did a conversion of the AV.
Many AV owners wanted SS version so they made their own with emblems, some had suspension changes and a few had a supercharger. Nothing official or in mass production was made. One of the performance companies would make a version with their logo and some interior changes as well as supercharging but you had to buy your own AV and send it to them for their touch on it. Not sure but maybe it was Street Legal Performance that would do the work.
Some AVs from certain states had option packages that they named for the state they were sold in such as a Texas Edition sold in Texas. But it was just a grouping of some factory options nothing really special.
Most of the wild custom AVs you can find on the internet is usually a one of design done by the owner not a group offered by a shop somewhere or the factory.