Big Block Cylinder Heads "915 vs 906"

Wow, I'm working on a 451 now for a really light dart. Was told it should be under 2500lbs with BB. I've got some 346 heads that were home ported years ago then sat on the shelf till now. What's it cost to get a set to flow well & including installing larger valves? I think it would be great to knock out some really low 10's with a stock crank, rods & iron heads. Thoughts?