If it is an original 428CJ car, that would be choice #1. They don't fall out of trees, but they are not unobtanium either. A good blueprint to factory specs, with adjustments for unleaded premium (hard seats, cam profile, etc) is a good 400 hp, sure as shootin.
Now, if a little browsing of these classifieds and ebay doesn't turn anything up, it would be a tossup between the 351 C and W. I like the more burly look of the -C; the new Edelbrocks just cinch the deal for me.
One of the Ford mags did a buildup with stock 351C4V heads and intake, and got 400 hp plus with a stroker crank and a .060 overbore.
The -W has so much available in the aftermarket, the only hard part is deciding what combo to use; I've seen the stories (believe how much you want of those) that put them north of 600 hp, but I wouldn't want to drive one to the supermarket.
429-460s make sick power but they require a whole driveline upgrade