If you make a half dozen phone calls you can find someone to sell you a 496HO for 13/14k. Crusader, Marine Power, Kodiak, and others all use "GM Powertrain" engines as their base platforms. These are excellent long block foundations and even the cheapest 2bbl carbed 350 has a hydraulic roller and vortec heads. Some companies do a better job of marinizing then others, and most have decent flowing cast aluminum exh manifolds. There is no issue regarding durability in a performance application, but unless you have a donor engine the same as the one you are upgrading to then you are out of luck for a lot of applications and have to buy all the stuff to adapt it from merc. None of those companies make drives, so they don't offer compatable bellhousings, no power steering on some, shift actuators, some wiring harnesses are pinned differently, etc... These are not difficult to adapt but will bring you right up to the cost of the merc, which you can bolt right in. If you need a drive it becomes even worse because merc stings ya if you buy things seperately rather then in a package and it will end up costing almost twice as much to mix and match. Finally on a service level every marina in america has a shop that will honor a merc warranty. But if ya want a turn key 425hp 496 I can sell ya one for $10,200, 6.0 with variable valve timing 375hp $9000, Or supercharged and intercooled 545hp 14k... All with the standard GM powertrain warranty.. whatever that's worth.