I agree with you, I have a 3.6L charger with the ZF8 and it's quick.
I'm going to be doing a 5.7/nag1 eventually to replace the 383/a500 in my Fury.
For my coronet, I am doing turbo 5.7/727 because it'll be 90% strip.

70 Sport Fury
68 Charger
69 Coronet
72 RR