Do some research, I know guys with the right intakes and drop mounts have fit them under stock hoods. Without drop mounts my headers had about 3 inches of clearance, so a cowl was the only option for me.
I have a 2 1/2 inch cowl and I still have some room. Mind you my 351w is carbed but it does have a 3 inch filter on it. the 2 1/2 inch cowl looks great IMO. before I installed this fiberglass hood I took a scoop off of a 83 gt and cut a hole in my hood then installed the scoop facing backwards. It was a very clean look. I think I liked that combo on my car better but I wanted the wieght savings.