The 6.4L crate engine is different (and much better) compared to the engines they put in the SRT vehicles like our Jeeps. The crates are good for all sorts of abuse with much less risk if you want to put any sort of FI on your car. They don't have some features though which our engines do, such as the ECO mode.
Prices are not cheap at all... keep in mind that their published performance figures are usually extremely conservative. Folks report getting much better numbers than advertised (similar to how our beasts put out more than expected.)
Mopar Pro Shop - Mopar Performance Parts (MoPowered) - PERFORMANCE ENGINES
If you want to play with the big boys you have to pay.