I have a 1998 ts770 with a blown engine. When it went, the rod tore both crank cases up. Therefore I have no core. I found a good 640 engine for $100 and want to know if it will fit in the 770 without major mods. Changing intake or exhaust manifolds is ok as the 640 comes with the complete ski minus a jet pump. I can mix and match parts from both so long as between the two of them I can get the 770 up and running again. Any info would be great seeing as how I've never messed with jet skis before and this is a new adventure. Thanks!