The C is my favorite - but currently walking away from it in the race cars. I ran a 393C, flat top, 12:1, 3.85 arm, 6" rod. Used AFD 4V heads, untouched - just put the valves in. They flow a little better, and certainly have a better chamber, than the 4V iron stuffed heads I have. 26 degrees of timing with a Lykins custom solid roller, 750DP, Funnelweb intake - made around 575+ on methanol. Until the block broke. We're going back with a 4.125 Dart "W" type block, 9.2 deck, 4" steel crank and new pistons for 427 CID. Should last a lot longer than three years.
For a street car, the HP figures are good for car shows and bench racing. If you plan to race one, get an aftermarket block. Once you take a stocker 302/351C/etc past around 500 HP you are on borrowed time. And 351C blocks were only made from 1970-74, so that's 46 years out of production. I have one 4 bolt std bore block left. If I use that, no more. Takes a good kit to stroke a 351C. For a W, a 9.5 deck 351W can use a 3.85 crank, a 351w rod and a 302 piston to make 393 CID. Pretty easy and cheap for a street brawler.