346s are easier for the do it yourselfer type to not screw up porting and actually gain some flow, they also do a little bit better at high lift but the difference is very very negligable. Basically 915/906/346/452s are all the same flow wise, 915s have closed chambers and 915/906 ports are the same and 346 and 452 ports are basically the same. Theyre all very close in flow and are what you want if youre going to run factory wedge heads from a passenger car.
Id loose the 509 too, not because I dont like the Mopar cams, but because I think its pointless to have that much duration with hydraulic lifters in a 440. If you want to run a DC cam try the .557 mechanical, its a little more agressive by spec but once you factor in the lash its not much different, Ive heard good things about it from a few people who have run it.
I also hear good things about the Comp 292 magnum for a similar cam. But the build youve laid out, 440, 10:1, DC509, torker, and a carb to support it with 1 7/8 headers has long been the default 500 hp 440 build.
