For the Banks turbo kit I just did a google search and a bunch of places still have it listed, but I also know that is not a 100% guarantee they are available. However it doesn't surprise me at all they stopped making the kit considering that engine hasn't been used a truck since the early '90's and it's not a popular retrofit by any means. As mentioned above there have been people that retrofitted 6.5 turbos, and I also believe they are correct regarding the AC box (which the CUCV does not have) and something about the long vs. short style injectors.
For some non-turbo improvements:
Stans Headers does have headers available for around $800. They claim big horsepower gains but I've always been pretty optimistic about this. I've also never been able to find any actual reviews on these. Over the years several people have posted on the diesel page on this site about how they bought them and would give a review but have never seen a follow up.
On my '90 K5 I've done the following: single port non-EGR intake that is ported/gasket matched (came of a Hummer), slightly turned up fuel pump (no black smoke thanks to increased air flow from the intake), and installed a set of Flowmaster 40 series with dumps with the stock size 2.25" pipes. I need to have the exhaust replaced and would like to go to 2.5" pipes and make adapters at the exhaust manifolds that don't neck down. I could also turn up the fuel pump a little more as I have basically zero black smoke (a lot of black smoke is just over fueling). Personally I think it runs decent. Bought it way back in '94 with 49k on the clock and all stock. It is now a dedicated off-road rig on 40" tires so I don't run it down the freeway or anything, but do sporadically drive it through time or on back roads. Even with 4.10 gears (TH700R4 trans) it runs okay for what it is.
Any suggestions on performance enhancing the 6.2 exhaust? Mine is OE I think and it is past due. Headers (yeah, right) Muffler choice, ready made complete kits etc.? Any info will be appreciated. 
