400 Non Stroker Build

I would start with a KB 240. (Hypereutectic i believe). High 8s to low 10s compression ratio, depending on heads and gaskets used. Get the compression figured out, and everything else is ordinary big block mopar techniques.
IQ52s low compression builds are awesome, but he is an awesome engine builder. Mine would not run that well.
As for the 440 pistons, you would need to find some with very thick piston heads, cause you would have cut at least .100 off the top of the piston.
KB240 compression height, 1.91, typical 440 ch is 2.02-2.06.
To the best of my knowledge, the only forged pistons available for a 400 block are stroker pistons.