The Ribeye A600 is a nice looking rib. Side by side jockeys, rear bench (nicely upholstered), etc. It can take up to 200kg engine weight maximum, so God knows why anyone would put a lardy 100hp on it? You know these things retail for anything from £18-25k?
If you're serious, then sell the 90hp. Most of these ribs will come with an engine as part of the package as that's how it would have been commissioned. There's one in Ireland with twin 50hp engines (words defeat me).
What's the chances of you running 10-up unless you're the equivalent of the Von Trapps?