I run my 250 with my 3x4 tunnle ram (450 holleys at 7-8) so you should be fine with the 5-6 The holley can handle up to 9 psi. so you want at least 5-6 at the top end (w/o).

Larry/Twisted6
[oooooo] smile
Adding CFM adds boost smile
shocked God doesn't like ugly.