I use the large 3x and -4 single four on many of our big wedge and hemis.We have tried the inline hemi manifold on one of our hemis with 2 800 Edelbrock carbs and best results so far is [Email]9.60@140[/Email] mph.It idles very clean and is very responsive for what I consider a street manifold. Ron McCelland runs a similar Stage Five manifold with 2 800s with the exact same results on his hemi.His combo is 528",4.30 gear at aprox 3700# 66 Cornet.