shah,
Keep in mind that the DP carb is simply a fuel mixer.......and that it can be tuned......you just need to find someone that understands the "mixer" and how to adjust the "recipe"!
I had a DP on my Boss 302 in my Mangusta. It was very well tuned! (Rest of the motor was Frankysteined by persons dorking with things after the initial setup!) It was cross jetted for proper performance of the fuel mixtures noted on the dyno.
I used the DuraSpark II ignition on the car and can only say from my experience that the fuel "cloud" was much reduced after a better ignition system was installed replacing the old points distributor.....which reminds me....what DID I do with that old distributor??? 
Probably worth something now!
The VS carb of any sort will be fine. Again a properly tuned VS carb will work very well on the 351C! But ya gotta know how to do it!
A How to Tune Holley Carbs by Dave Emanuel would be a great book for your nighttime reading habits!!! The basic carb hasn't changed much since the original one barrel carbs if you get right down to it! Only thing has changed is how many one barrels do you pack into a single piece!??
It's all about venturi flow, proper vacuum signals, and metering of fuel....probably a few other things, but the basic carb is just a mixer....
What IS amazing is that it took all of the computing power and bits and pieces of EFI to finally MATCH power levels that could be had from a carb based design from decades before. The old timers did a good job! (Note, not talking about drivability here......)
Cheers!
Steve