Re: That Ford Sound
Header selection, catalytic converter and muffler designs, and pipe size all play a big role in the tone of the exhaust. Headers with individual primaries (as opposed to stock manifolds, also referred to as "logs", which collect all the gases together as soon as it exits the head) will enhance the "pulsing" of the exhaust- you'll have more of a growl than a rumble, if that makes sense.
Catalytic converters (not gutted, of course) will tone down that growl (which can easily sound like a popping on too large of a pipe diameter) because they provide the resistance and give the exhaust gases a very brief moment to collect together.
Muffler design probably plays the most part in the tone, though. If you use a straight-through design, the gases will be able to come straight out and the pulsing of each cylinder firing will be significantly more noticeable. The baffled designs allow the exhaust gases to linger a moment, providing them an opportunity to blend together and reduce that pulsing sound while also providing improved backpressure/torque over a straight-through design.
I'm running shorty headers, gutted cats, and baffled mufflers (Flowmaster; don't waste your money on 'em). It's loud (no tailpipes), but it's very toned. I love it, but I do plan to have it redone with some mufflers that aren't crap. Once it's back on the road I'll get a video clip and post it up.
On a 351C, I'd recommend some good shorty headers, no cats, an X-pipe, and some sound baffled mufflers. I've heard great things about Edelbrock's new SDT designs. You may want to give them a try. They're a little pricey, but any good muffler will be. Again, do not waste your money on Flowmaster.
Pipe size ultimately depends on your power level. Most mild to moderate V8s will benefit most from a dual 2.5" system with a crossover. Blown and juiced cars often go with a larger exhaust, but you'll rarely see a street car running anything bigger than dual 2.5".
I hope that helps a little bit!