Why not build a 340?

I want as much usable hp as I can get. I estimated the 318 would put out between 270-300 to the wheels. Going to have pro trans (local drag racer) build the 904, he suggested putting in a lower first gear and use a 323 rear end, rebuild the stock torque converter. The lower first gear will have a ratio similar to a 355 rear end. Good out of the hole but not be spinning so high on freeway. I trust his opinion on this, he IS the 904 go to guy. This is intended to be a fun street rod, not a race car.