stock 69 nova gastank leaking fuel?

like stated, the tank on my nova is leaking bad when i go all out, were talking a stream of fuel. i replaced the gastank gap and still nothing. this is a perfomance rebuild, basically only thing i havent messed with is the gastank.
any idea's what i should try? its clearly leaking behind the cap.

The license-plate fill neck is notorious for leaking under accel. because it's so low -- if your Nova squats in the rear, the neck could end up below the tank level -- there should be some baffling in the neck to help prevent spillage, but it's kind of difficult to install if it's not there already. There may also be vent holes in the neck near the cap that may be where the leak is coming from.