I,m am building a hand made tunnel for a 572 hemi . I am trying to maximize it , plenum volume , runner taper ,round runner vs square runners . What is the best aluminium alloy to build it from. I have 3100 lbs dart . I red line it at 7500 rpm. The convertor flashes to about 5700 rpm . I am currently running a indy tunnel ram with 2 850 cfm quick fuel carbs .