I'm not %100 sure, but with a stock 400 in a heavy 73 Charger with 3.91's, maybe 5.5 or 6 seconds? You'd need decent traction, and probably a higher stall torque converter to get there.

Your goal is doable though I think. Especially if you go the 470 or even a 505 route since it really doesn't cost much more.

Speed cost money, how fast you wanna go?