I've run a Class II Hidden Hitch on my FWB for 15 years. Thoughts on it are it's perfect for my needs with 300# tongue and 3,500# gross. The little trapazoid plastic cover hid it pretty well. I never had reason to haul anything 6,000# with the car to warrant a Class III. Sounds like you've done researching, but I think there's been a good deal of consolidation/Part No. changes and general shuffling of brands Reese-Hidden Hitch etc.. And definitely options dying for our aging tub.
An Impala SS is just a Caprice with different trim options. And you know to keep lotsa wt. on the tongue to keep from whiplashing. Those are always fun to watch - from well behind.
\'96SS SOB: SSRI, Herter Tune, Tri-Y II, , 3000 Edge, F/HO bars, METCO extendeds with CV MMC, Bilsteins, currently Vredestein Ultrac Sessanta (315/35 rear). Finally, wait for it... LT-4 knock module!
\'96FWB BUW-Butt Ugly White: PCMPerformance tune, HDFA w/ swissed filter, 1/2 SLP s.s. catback with H- and Flow Super 50s, oem opti rebuilt 3 times, SS Bars, METCO LCA, Airlift 1000, Monroe SS, PowerTrax No-Slip, CTS wheels with +1 rubber. Finally, yes again... LT-4 knock module!