If anyone wondering for final clarification on motor confusion above: 300R is naturally aspirated V8. 400R is super charged small block verado. 450R is super charged big block V8.
Further clarification.
The 400R is an inline 6 cylinder with supercharger.
The 450R is a V8 with supercharger.
My guess is Merc will kill the 400R and offer the naturally aspirated 300R as a 350R in the next year or so. They already offer a 430# version @ 360 HP for tunnel hull racing that runs on pump super unleaded. This motor is supposed to be, "Available to qualified race teams" only but what it should say is, "Anybody with $48,000"
There is no reason to have a 700 pound 400 HP six cylinder when you already have a 700# 450 HP motor that runs on pump 89 octane.