What Can Be Dome With a Chrysler 400?

Streetmaster is a good intake. 400 motors were pretty low compression, but basically a bored 383. If the stock pistons are in there, you can bump the compression by putting on some #915 heads off a '67 only 440" motor. They had big valves and small, closed combustion chambers. Then make sure you have a good street cam with around 230 degrees @050. I' ve seen some crazy mis-matched cams that guys just label "race cam" or the famous "3/4 cam" .I'd add a MP electronic distributor too. Very few ( if any) Durangos had 4.11 gears. I've sold tons of them and never seen one yet. That rear has an inspection cover, or you can just jack it spin the wheeels to figure the ratio. The lowest stock ratio was a 3.92 that came in a R/T. The rest had 3.55's. I'd choose 3.92 for kickin' butt or 3.55's for a more cruise friendly ratio. Make sure the carb (a 750 vacuum would be best)is tuned good and you should have great package. Looks like a clean install!