You are brave for taking this on. No expert by a LONG shot but I'd opt for a 300 hp 2 stroke on a notched 30" transom with the splashwell (make the splashwell foldable to give you as much stern room as possible). Then float her and see how she sits. From there you can add/subtract weight along the centerline as needed. Use a 6 gallon portable tank and bring weight to simulate tank placement, etc...Seems the best strategy for doing it once
Best of luck, Steve