On the far other end are the Toyota boat engines. Many of those Northstar traits but in a real small displacement - 4.0L. 300HP and 315 ft/lbs. I just averaged 3.3 GPH over 30 engine hours at Havasu. This was not all channel cruising, and we did do a lot of over 30mph cruising and some lightly-ballasted riding. My normal consumption is under 4GPH with a small crew and 1600 pounds. Pretty sure no 8.1 is gonna ever touch that.
OTOH, if you like to ride with a pro wake, my little Lexus will never satisfy you, and it'd never push the big new boats out of the hole. It got 3000 pounds out with a stock prop, but the third guy in the boat had to walk forward ;-)
It seems hard to me that anyone would pass up implementing things like variable valve timing, quad cams, hemi, distributorless ignition, 10.5:1 compression, etc. in any size engine. Mine's all-aluminum which is cool in terms of cooling and trailering, but bad if you like running in salt.
It'd be great to have all this stuff with a 5.7L, fo sho, but to just throw a zillion pushrod, two-valve cubic inches at the problem can't be good for fuel economy. My vote's for Northstar.