Opinions please- new hemi or 408?

I'm still building mine, so I can't offer experience, yet. I did check out your build, very nice Duster you've got there. A warmed over 5.7 with eagle heads or a 6.1 with ported heads, a mild camshaft .219/.223 @ .050 with headers should put down about 420-440 HP @ the wheels, run without issue on pump gas and manage 20MPG on a cruise. In other words, it should make almost the same power as a warmed over 408 LA. My ported 6.1 heads flow between 340-348cfm from .550-.600 lift.

If you go with the 5.7, mock it up with the transmission and headers as it's a pretty tight fit. Good luck and I look forward to following your build.