I sold a mostly full used kit for $3000 with a banks turbo rebuild kit that is no longer available. The banks kits are worth a lot and are still the best turbo set you could get for a 6.2 and even a 6.5!
Also sold 2 partial Banks kits for $800-$1500.
Last I checked with Banks they still sell some parts of the kit but they are getting limited. They have only 15 Banks Exhaust Manifolds left as of 2021. They quit selling the turbos many many years ago.
When you call Banks you must get the right technician in regards to the Banks kit parts. The newer noob technicians don’t know what they have on their shelfs.
My recommendation is don’t buy a banks sidewinder kit because parts are limited or are no longer available. The rebuild kits for these turbos are simply gone! I bought the last one on eBay. Unless there is a lucky find on a rebuild kit.
My advice is to simply buy 6.5 turbo parts because they are super cheap, can be found anywhere in the junkyards, a plethora of upgrade options and can be tuned easier. With 3 banks turbo kits at my disposal, I went with the 6.5 Turbo parts route for my Optimizer because if I need to replace parts, I can simply drive a couple blocks down the road to the junkyard and get what I need to replace it cheap and fast!