Chris:

This is what I would do...

Use a stock replacement block, (unless you have the WP block already and are committed to using it). Put a 4.15 stroke crank and a solid roller or just a plain solid cam. Little port work on the heads and run a Rat Roaster and a pair of Competition series Carters. Set of TTI 2-1/4" headers.

Should EASILY run the number, and you will have the Nostalgia look covered. I am fully aware that there are much better combos out there, this would really look cool on a car like your Challenger

MB