I'm about to install a used MK IV 454 in my stepson's 23' WebbCraft Velota. He scarfed a donor boat with this thing in it, and the very first thing I see, as he's backin' under the hoist, is the coupler splines are skinny. His dead 330 hp 454 had a 3 bolt triangular plated coupler, the replacement engine had a 6 bolt round coupler. The replacement 454 also has an Iskendarian Megahydraulic 281 cam, Edlebrock airgap intake, and Edlebrock 1410 marine carb. Am I risking him blowing the azz off this rig, letting him run it this way?