Don't know about cheaper, since the 380hp crate is the same as a 5.9l from a junk yard just with an aftermarket cam and intake.
Saying that I'm not knocking the 318/390 it's a cool little build most be happy with especially with a set of headers, just thought if you were thinking about a 318/390, just letting you know you could get there basically with a 360, after that choice is yours.