Love the '66 Belvedere! I ran a 4-speed '67 GTX with a serious HEMI (12.5:1, etc. Spun it off a 600 HP dyno at the machine shop with 1,000 RPM to spare); low-to-mid 11 second car, restricted by terrible street rubber choices at the time. Stepping into that second 4-barrel at ~4,000 RPM was a unique experience with 14" wheels and a 4:10 rear end. (Not unlike the GEN IV Viper @3,800 in first.) Handled like a school bus - no power steering - and stopped nearly as well, but made me smile every time I fired it up.
I bought a new '08 SRT10 Coupe last year and re-experienced the joy of pure HP and big cubes, but now I can actually turn and stop the car on demand. After 15,000 miles I can say without reservation that this car would stomp my old HEMI yet it still delivers raw 'muscle car' feedback and an even greater adrenalin buzz thanks to its handling capabilities. I believe the Viper is the only true American muscle car left and am certain you'll grow to appreciate the evolution of MOPAR engineering from your '66 to the present-day Viper. I particularly love the TREMEC 6-speed (vs. rowing the tow-truck 4-speed they hooked up to the old HEMI).
The lesson I learned quickly with the Gen IV Viper is that it comes as advertised: it goes exactly where it's pointed and, unless you're going in a straight line, getting on the gas or brakes hard can lead to misfortune; exercise some restraint. I keep 2 hands on the wheel.
If you haven't been to a track, try to get out to one: you will enjoy this machine like nothing you've ever driven before. It's also an awesome highway cruiser and, so far, as reliable as my wife's Honda.