I have no experience with the Challengers or the Hemi, but I messed with some of the LS1 stuff a few years ago and going from my experience drag radials and a converter in an auto is going to be the most bang for the buck. I had a WS6 Formula that went 7.89 at 87 mph in the 1/8th with those two changes.

Getting old just means you were smarter than some and luckier than others.