If you are set on a 408, you should have all kinds of torque, so the next problem becomes what do I need to make it bullet proof. I'd get a Passon Hemi O/D,
http://www.passonperformance.com/images/stories/passon_documents/Passon_Overdrive_Flyer_20091109.pdf, and be done. You can use standard "A" Body shifter, linkage and all. The rear will be the next weak point. What torque are you looking at?
