Tf 240 head will be fine , TF270 will be better and more power . In my motor was worth 0.25 of second or about 40-50hp .
If you cant get a Super Victor max wedge you can port the standard port Super Victor to max wedge , i did that . Not sure if Victor will go max wedge
Loss of torque ? You have a 4.25 stroke 511ci motor .
Flat tappet is simple and durable , again thats what i run .
I have pump gas 11:1 premium gas .
Idles @ 925 in gear in traffic no worries , summer or winter .
Dual quad ? Try a modman , wont choke it like eddy unit , and has enough meat to go max wedge . Run 2 x eddy 600s or 800 eddy AVS

Tex