There is a lot of ways to go 9s in a Duster, but you asked for the best. Hands down, 572 pump gas Hemi. Red line it at 6800 and it will live forever, cheap to operate, huge resale value compared to anything else. And the whole range of 9's is available, from 9.000 on up. There really is not reason NOT to go with a Hemi.
A 416 with Indy heads in a 300-3200 pound A body will dip well into the 9’s shifting it 6800-7000 grand too.
Had a similar to the above W5 deal i shifted at 7000 that i had hundreds and hundreds of passes on it at 3350 pounds that it took a very hot day for it to run 10 flat, beforei sold the car.
Had 1/2 the money it it a hemi would cost, and not the extra weight on the nose
