I'm doing exactly as many of you have written. However, I've taken a little different approach to the driveability of the car instead of getting crazy on horsepower. I have a '73 Challenger, swapped the Keisler TKO 5 speed in last summer, 408 small block, worked the suspension a little to handle decent....notice I did not say great. Old Mopars need help cornering.
The direction that I would take is definitely into the EFI world with any old mopar, the start and throttle response is superior to any carb'd set-up. Supercharging and EFI is way cool but brings a host of upgrades that must be done to support the installation, ie bottom end, blower pistons, roller valve train...it all adds up to an expensive package for track or street.
Another direction may be the 425 horse, 6.1 L Hemi. They will eventually make it to a scrap yard near you! Mount a supercharger onto the front an go eat a few Camaro's. (sorry to the chebbie owners)
How about this... stroked small block, EFI, old school Mr. Norms GSS Paxton supercharger on top for the newstalgia flare (Big, flat black bonnet and all), 5 or 6 speed for the freeway driving and of course AIR CONDITIONING. My 2 cents.