I wouldn't say they've "completely redesigned" the hellcat motor, they sleeved a 392 to make it beefier to handle the boost, which resulted in a 200cc reduction in total engine size, which makes it a 6.2 instead of a 6.4
fairly close to a redesign.
http://blog.caranddriver.com/ten-shades-of-hell-10-things-we-learned-about-the-stonking-707-hp-hellcat-v-8/ Revelation 1: While this Hemi is a cousin to 5.7-, 6.1-, and 6.4-liter Chrysler-built V-8 engines, the Hellcat is, for all intents, a new design sharing only basic architecture—such as a 103.9-mm bore—with its predecessors.
More than 90 percent of the components (by value, not parts count) are new. The cast-iron block has thicker webs and larger cooling passages to support the added power and stress. The induction-hardened forged-steel crankshaft provides the desired 90.9-mm stroke. The powder-forged steel connecting rods have cracked bearing caps for more secure clamping. New forged-aluminum pistons withstand more than 21,000 pounds of combustion pressure. The 24-mm wrist pins have a diamondlike coating for minimal friction.
and to comment on the other "Largely stock aside from the addition of a Kenne Bell supercharger package..." ..... there is a reason FCA made the hellcat motor much beefier. a standard engine with no beefier components will fail much quicker.