To me much depends on how much street and or race you plan to use it. And as many said with that big Hemi you dont need as much gear as it should have the torque to pull about the same et with lower number gears. Of course if you plan to race it and put sticky tires on it then I would go with a Dana or Ford 9" with the manual trans. I also agree it will work better with a taller tire. I run a 30" tall tire on my 63 with a 440/493 wedge that I am sure makes alot les power then your Hemi and the 30" tires work nice for me at the track and on the street. If you plan to race alot I would go with about a 30" tire and run 3.91's with your combo. Good luck what ever you decide on. Ron