I think you are better off just grabbing a used or reman 6.1L modern Hemi with a 6 speed tranny and 3.55 rear gears
Bone stock in your car and it will do 0-60 in around 3.5 secs, 1/4 mile in 11.5 secs and 0-100 in 9 secs. And it will get 20 mpg on the highway.